1kHz 130dB distortion sinewave oscillator.

But at least I know what mine are doing.

This is a strange circuit. One problem with using an N-channel junction fet like J113 is that if you bias the gate at a higher voltage than the source or drain, it acts as a diode and feeds current into the channel.

I've downloaded and run the second version of the simulation, and the gate doesn't seem to end up more negative than the source or drain.

It takes quite a lot of simulation time before the circuit starts acting as if were an amplitude controlled oscillator, and I'm not interested enough to try and work how it is actually working.

"Bill Sloman" snipped-for-privacy@ieee.org wrote in message news:vnim5i$3hnrj$ snipped-for-privacy@dont-email.me...

After tweaking a few component values, I get -130dB with the circuit below on LTSPice 24.1.1

Simulate to 20s and take a sample near 20s. FFT on current zoom extent with Blackman-Harris window.

Zoom in on 1kHZ and 2kHz. Place cursors to get difference. -130.7 dB give or take a dB. All other harmonics are lower.

Also if you make a trace for V(gate)-V(src) you find it's -675mV at 20s so as far as I can tell the FET is operating conventionally and in the centre of its control range. If it goes positive at all it's only during the first 10ms but amost anything can happen with this circuit during the first 10ms.

Getting below -130dB will likely require another four rectifier phases so that the signal at the node named levelfb reduces by half again.

If you can come up with a suitable eight phase rectifier let me know, particularly if it doesn't require DC stabilization of every phase to get the contribution through all eight diodes equal.

After all, I spent a lot of time figuring out that the reason why your circuit doesn't simulate in 24.1.1 is something to do with LT1115 but I still don't know exactly what.

This circuit uses LT1115 but only for the oscillator. The rectifier and level controller can use TL084 or similar.

Version 4.1 SHEET 1 3828 932 WIRE 976 -816 816 -816 WIRE 1056 -816 1056 -848 WIRE 880 -752 880 -768 WIRE 976 -736 976 -816 WIRE 976 -736 912 -736 WIRE 816 -720 816 -816 WIRE 816 -720 720 -720 WIRE 848 -720 816 -720 WIRE 1056 -704 1056 -736 WIRE 1056 -704 912 -704 WIRE 336 -672 256 -672 WIRE 480 -672 400 -672 WIRE 720 -672 720 -720 WIRE 1056 -672 1056 -704 WIRE 1168 -672 1056 -672 WIRE 880 -656 880 -688 WIRE 1056 -656 1056 -672 WIRE 1168 -640 1168 -672 WIRE 256 -576 256 -672 WIRE 336 -576 256 -576 WIRE 480 -576 480 -672 WIRE 480 -576 416 -576 WIRE 1056 -544 1056 -576 WIRE 1168 -544 1168 -576 WIRE -192 -480 -192 -512 WIRE 384 -464 384 -480 WIRE 480 -448 480 -576 WIRE 480 -448 416 -448 WIRE 576 -448 480 -448 WIRE 640 -448 576 -448 WIRE 720 -448 720 -592 WIRE 720 -448 640 -448 WIRE 1168 -448 720 -448 WIRE 1664 -448 1168 -448 WIRE 2256 -448 1664 -448 WIRE 256 -432 256 -576 WIRE 352 -432 256 -432 WIRE 448 -416 416 -416 WIRE 464 -416 448 -416 WIRE 576 -400 576 -448 WIRE 1168 -400 1168 -448 WIRE 1664 -400 1664 -448 WIRE 2256 -400 2256 -448 WIRE -416 -384 -416 -480 WIRE -336 -368 -336 -400 WIRE 384 -368 384 -400 WIRE 1376 -368 1328 -368 WIRE 1520 -368 1456 -368 WIRE 1968 -368 1920 -368 WIRE 2112 -368 2048 -368 WIRE 16 -352 -144 -352 WIRE 576 -288 576 -320 WIRE 1168 -288 1168 -320 WIRE 1664 -288 1664 -320 WIRE 2256 -288 2256 -320 WIRE -336 -272 -336 -304 WIRE -80 -272 -80 -304 WIRE 1328 -272 1328 -368 WIRE 1376 -272 1328 -272 WIRE 1520 -272 1520 -368 WIRE 1520 -272 1440 -272 WIRE 1920 -272 1920 -368 WIRE 1968 -272 1920 -272 WIRE 2112 -272 2112 -368 WIRE 2112 -272 2032 -272 WIRE -144 -256 -144 -352 WIRE -112 -256 -144 -256 WIRE 16 -240 16 -352 WIRE 16 -240 -48 -240 WIRE 48 -240 16 -240 WIRE 64 -240 48 -240 WIRE 256 -240 256 -432 WIRE -192 -224 -192 -400 WIRE -112 -224 -192 -224 WIRE -416 -208 -416 -304 WIRE 976 -192 880 -192 WIRE 1168 -192 1168 -224 WIRE 1168 -192 1040 -192 WIRE -192 -176 -192 -224 WIRE -192 -176 -256 -176 WIRE -80 -176 -80 -208 WIRE 1408 -160 1408 -176 WIRE 2000 -160 2000 -176 WIRE -192 -144 -192 -176 WIRE 1328 -144 1328 -272 WIRE 1328 -144 1264 -144 WIRE 1376 -144 1328 -144 WIRE 1920 -144 1920 -272 WIRE 1920 -144 1856 -144 WIRE 1968 -144 1920 -144 WIRE -256 -128 -256 -176 WIRE 1520 -128 1520 -272 WIRE 1520 -128 1440 -128 WIRE 1664 -128 1664 -224 WIRE 1664 -128 1520 -128 WIRE 2112 -128 2112 -272 WIRE 2112 -128 2032 -128 WIRE 2256 -128 2256 -224 WIRE 2256 -128 2112 -128 WIRE 1264 -112 1264 -144 WIRE 1376 -112 1328 -112 WIRE 1856 -112 1856 -144 WIRE 1968 -112 1920 -112 WIRE 448 -96 384 -96 WIRE 576 -96 576 -224 WIRE 576 -96 512 -96 WIRE 880 -96 880 -192 WIRE 976 -96 880 -96 WIRE 1168 -96 1168 -192 WIRE 1168 -96 1056 -96 WIRE 208 -80 160 -80 WIRE 256 -80 256 -160 WIRE 256 -80 208 -80 WIRE 1408 -64 1408 -96 WIRE 2000 -64 2000 -96 WIRE -256 -32 -256 -64 WIRE -192 -32 -192 -64 WIRE 160 -32 160 -80 WIRE 384 0 384 -96 WIRE 448 0 384 0 WIRE 576 0 576 -96 WIRE 576 0 528 0 WIRE 880 0 880 -96 WIRE 928 0 880 0 WIRE 1040 0 1008 0 WIRE 1168 0 1168 -96 WIRE 1168 0 1120 0 WIRE 256 64 256 -80 WIRE 464 96 464 80 WIRE 128 112 112 112 WIRE 160 112 160 48 WIRE 160 112 128 112 WIRE 192 112 160 112 WIRE 304 112 288 112 WIRE 336 112 304 112 WIRE 384 112 384 0 WIRE 384 112 336 112 WIRE 432 112 384 112 WIRE 960 112 960 96 WIRE 576 128 576 0 WIRE 576 128 496 128 WIRE 640 128 576 128 WIRE 672 128 640 128 WIRE 752 128 736 128 WIRE 880 128 880 0 WIRE 880 128 832 128 WIRE 928 128 880 128 WIRE 400 144 384 144 WIRE 432 144 400 144 WIRE 1168 144 1168 0 WIRE 1168 144 992 144 WIRE 1328 144 1328 -112 WIRE 1760 144 1328 144 WIRE 1920 144 1920 -112 WIRE 2352 144 1920 144 WIRE 928 160 880 160 WIRE 112 192 112 112 WIRE 192 192 112 192 WIRE 336 192 336 112 WIRE 336 192 272 192 WIRE 464 192 464 160 WIRE 960 208 960 176 WIRE 640 256 640 128 WIRE 1264 256 1264 -32 WIRE 1264 256 640 256 WIRE 112 288 112 192 WIRE 192 288 112 288 WIRE 336 288 272 288 WIRE 464 288 416 288 WIRE 1168 288 1168 144 WIRE 1168 288 464 288 WIRE 1856 288 1856 -32 WIRE 1856 288 1168 288 WIRE 2432 288 1856 288 WIRE 2560 288 2512 288 WIRE 2720 288 2624 288 WIRE 2784 288 2720 288 WIRE 880 352 880 160 WIRE 1168 352 880 352 WIRE 1664 352 1664 -128 WIRE 1664 352 1344 352 WIRE 2256 352 2256 -128 WIRE 2256 352 1936 352 WIRE 2784 352 2784 288 WIRE 640 368 640 256 WIRE 720 368 640 368 WIRE 464 400 464 288 WIRE 640 400 640 368 WIRE 720 400 720 368 WIRE 1344 400 1344 352 WIRE 1936 400 1936 352 WIRE 2784 448 2784 432 WIRE 1024 480 1008 480 WIRE 1056 480 1024 480 WIRE 1168 480 1168 352 WIRE 1168 480 1136 480 WIRE 1600 480 1568 480 WIRE 1648 480 1600 480 WIRE 1760 480 1760 144 WIRE 1760 480 1728 480 WIRE 2192 480 2160 480 WIRE 2240 480 2192 480 WIRE 2352 480 2352 144 WIRE 2352 480 2320 480 WIRE 640 512 640 480 WIRE 720 512 720 480 WIRE 720 512 640 512 WIRE 464 528 464 480 WIRE 640 528 640 512 WIRE 1344 528 1344 480 WIRE 1936 528 1936 480 WIRE 848 544 832 544 WIRE 1024 544 912 544 WIRE 1440 544 1424 544 WIRE 1616 544 1504 544 WIRE 2032 544 2016 544 WIRE 2208 544 2096 544 WIRE 944 624 944 592 WIRE 1536 624 1536 592 WIRE 2128 624 2128 592 WIRE 464 640 464 592 WIRE 832 640 832 544 WIRE 832 640 464 640 WIRE 912 640 832 640 WIRE 1344 640 1344 592 WIRE 1424 640 1424 544 WIRE 1424 640 1344 640 WIRE 1504 640 1424 640 WIRE 1936 640 1936 592 WIRE 2016 640 2016 544 WIRE 2016 640 1936 640 WIRE 2096 640 2016 640 WIRE 464 656 464 640 WIRE 464 656 320 656 WIRE 1024 656 1024 544 WIRE 1024 656 976 656 WIRE 1056 656 1024 656 WIRE 1168 656 1168 480 WIRE 1168 656 1136 656 WIRE 1616 656 1616 544 WIRE 1616 656 1568 656 WIRE 1648 656 1616 656 WIRE 1760 656 1760 480 WIRE 1760 656 1728 656 WIRE 2208 656 2208 544 WIRE 2208 656 2160 656 WIRE 2240 656 2208 656 WIRE 2352 656 2352 480 WIRE 2352 656 2320 656 WIRE 640 672 640 592 WIRE 912 672 640 672 WIRE 1504 672 1456 672 WIRE 2096 672 2048 672 WIRE 464 704 464 656 WIRE 464 704 416 704 WIRE 640 704 640 672 WIRE 640 704 592 704 WIRE 1168 704 1168 656 WIRE 1344 704 1344 640 WIRE 1344 704 1296 704 WIRE 1760 704 1760 656 WIRE 1936 704 1936 640 WIRE 1936 704 1888 704 WIRE 2352 704 2352 656 WIRE 464 720 464 704 WIRE 640 720 640 704 WIRE 944 720 944 688 WIRE 1344 720 1344 704 WIRE 1536 720 1536 688 WIRE 1936 720 1936 704 WIRE 2128 720 2128 688 WIRE 416 736 416 704 WIRE 592 736 592 704 WIRE 1296 736 1296 704 WIRE 1888 736 1888 704 WIRE 1168 784 1168 768 WIRE 1760 784 1760 768 WIRE 2352 784 2352 768 WIRE 416 832 416 800 WIRE 464 832 464 800 WIRE 464 832 416 832 WIRE 592 832 592 800 WIRE 640 832 640 800 WIRE 640 832 592 832 WIRE 1296 832 1296 800 WIRE 1344 832 1344 800 WIRE 1344 832 1296 832 WIRE 1888 832 1888 800 WIRE 1936 832 1936 800 WIRE 1936 832 1888 832 WIRE 464 864 464 832 WIRE 640 864 640 832 WIRE 1344 864 1344 832 WIRE 1936 864 1936 832 WIRE 320 912 320 656 WIRE 1456 912 1456 672 WIRE 1456 912 320 912 WIRE 2048 912 2048 672 WIRE 2048 912 1456 912 FLAG 384 -480 V+ FLAG 464 80 V+ FLAG 960 96 V+ FLAG 208 -80 gate FLAG 128 112 drn FLAG 2784 448 0 FLAG 2720 288 output FLAG -416 -208 0 FLAG 384 -368 0 FLAG 464 192 0 FLAG 960 208 0 FLAG -416 -480 V+ FLAG 448 -416 half FLAG 400 144 half FLAG 1024 480 half FLAG -80 -176 0 FLAG -80 -304 V+ FLAG 48 -240 half FLAG -192 -32 0 FLAG -192 -512 V+ FLAG -256 -32 0 FLAG 304 112 src FLAG 880 -768 V+ FLAG 880 -656 0 FLAG 1056 -544 0 FLAG 1056 -848 V+ FLAG 1168 -544 0 FLAG 1168 784 0 FLAG 464 864 0 FLAG 944 592 V+ FLAG 944 720 0 FLAG 1408 -176 V+ FLAG 1408 -64 0 FLAG 1600 480 half FLAG 1760 784 0 FLAG 1344 864 0 FLAG 1536 592 V+ FLAG 1536 720 0 FLAG 2000 -176 V+ FLAG 2000 -64 0 FLAG 2192 480 half FLAG 2352 784 0 FLAG 1936 864 0 FLAG 2128 592 V+ FLAG 2128 720 0 FLAG 640 864 0 FLAG -336 -272 0 FLAG -336 -400 V+ FLAG 640 -448 levelfb SYMBOL njf 192 64 M90 WINDOW 0 -37 23 VRight 2 WINDOW 3 -9 -3 VRight 2 SYMATTR InstName J1 SYMATTR Value J113 SYMBOL voltage -416 -400 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 135 Left 2 WINDOW 0 10 0 Left 2 WINDOW 3 15 104 Left 2 SYMATTR InstName V2 SYMATTR Value 36 SYMBOL schottky 1184 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D2 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 176 176 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 22 SYMBOL res 176 -48 M0 WINDOW 0 38 42 Left 2 WINDOW 3 36 66 Left 2 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL res 272 -144 R180 WINDOW 0 40 70 Left 2 WINDOW 3 45 42 Left 2 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL res 320 -560 R270 WINDOW 0 33 55 VTop 2 WINDOW 3 -3 55 VBottom 2 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL res 1184 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R6 SYMATTR Value 470k SYMBOL cap 400 -688 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 10000n SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM185R60J106ME15" type="X5R" SYMBOL res 1072 -112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R9 SYMATTR Value 15k SYMBOL res 848 112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R12 SYMATTR Value 8.2K SYMBOL cap 1040 -208 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 10n SYMATTR SpiceLine V=16 Irms=647m Rser=0.0322889 Lser=0 mfg="KEMET" pn="C0201C103K4PAC" type="X5R" SYMBOL cap 736 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 22n SYMATTR SpiceLine V=4 Irms=356m Rser=0.150334 Lser=0 mfg="KEMET" pn="C0402C223K7PAC" type="X5R" SYMBOL res 544 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value 10k SYMBOL cap 512 -112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 22p SYMATTR SpiceLine V=16 Irms=0 Rser=0.3482 Lser=551p mfg="Würth Elektronik" pn="885012006019 WCAP-CSGP 0603" type="NP0" SYMBOL res 432 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R14 SYMATTR Value 1371 SYMBOL res 704 -688 R0 SYMATTR InstName R17 SYMATTR Value 470k SYMBOL res 2528 272 R90 WINDOW 0 -4 57 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 600 SYMBOL res 2800 448 R180 WINDOW 0 47 75 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R8 SYMATTR Value 600 SYMBOL res -208 -384 M180 WINDOW 0 40 70 Left 2 WINDOW 3 37 41 Left 2 SYMATTR InstName R5 SYMATTR Value 100k SYMBOL res -208 -48 M180 WINDOW 0 40 70 Left 2 WINDOW 3 38 43 Left 2 SYMATTR InstName R10 SYMATTR Value 100k SYMBOL cap -240 -64 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C1 SYMATTR Value 10n SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R" SYMBOL cap 2624 272 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL res 1024 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R11 SYMATTR Value 150k SYMBOL res 288 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R15 SYMATTR Value 8.2k SYMBOL res 1136 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R16 SYMATTR Value 47k SYMBOL OpAmps\\LT1058 -80 -304 R0 SYMATTR InstName U5 SYMBOL OpAmps\\LT1058 384 -496 M0 SYMATTR InstName U6 SYMBOL OpAmps\\LT1058 880 -784 M0 WINDOW 0 -79 26 Left 2 WINDOW 3 -120 114 Left 2 SYMATTR InstName U1 SYMBOL res 1040 -832 R0 SYMATTR InstName R19 SYMATTR Value 91k SYMBOL res 1040 -672 R0 SYMATTR InstName R20 SYMATTR Value 120k SYMBOL cap 1152 -576 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C7 SYMATTR Value 10n SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R" SYMBOL OpAmps\\LT1115 464 64 R0 SYMATTR InstName U4 SYMBOL OpAmps\\LT1115 960 80 R0 SYMATTR InstName U3 SYMBOL schottky 592 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D1 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 592 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R18 SYMATTR Value 470k SYMBOL schottky 656 528 M0 SYMATTR Value BAS40HY SYMATTR InstName D5 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 624 704 R0 SYMATTR InstName R21 SYMATTR Value 820k SYMBOL schottky 480 528 M0 SYMATTR Value BAS40HY SYMATTR InstName D6 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 448 704 R0 WINDOW 0 39 28 Left 2 WINDOW 3 41 58 Left 2 SYMATTR InstName R22 SYMATTR Value 820k SYMBOL res 1152 464 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R23 SYMATTR Value 100k SYMBOL OpAmps\\LT1058 944 592 R0 SYMATTR InstName U2 SYMBOL res 1040 640 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R24 SYMATTR Value 820k SYMBOL cap 608 736 M0 WINDOW 0 27 51 Left 2 WINDOW 3 21 77 Left 2 SYMATTR InstName C9 SYMATTR Value 1000n SYMBOL cap 432 736 M0 SYMATTR InstName C10 SYMATTR Value 1000n SYMBOL cap 1184 768 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C8 SYMATTR Value 1000n SYMBOL res 656 496 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R25 SYMATTR Value 10k SYMBOL res 480 496 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R26 SYMATTR Value 10k SYMBOL res 1280 -128 M0 SYMATTR InstName R27 SYMATTR Value 1.5k SYMBOL cap 1440 -288 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C12 SYMATTR Value 100n SYMBOL schottky 1680 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D3 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1680 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R36 SYMATTR Value 470k SYMBOL res 1472 -384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R29 SYMATTR Value 100k SYMBOL schottky 1360 528 M0 SYMATTR Value BAS40HY SYMATTR InstName D8 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1328 704 R0 SYMATTR InstName R31 SYMATTR Value 820k SYMBOL res 1744 464 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R32 SYMATTR Value 100k SYMBOL OpAmps\\LT1058 1536 592 R0 SYMATTR InstName U8 SYMBOL res 1632 640 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R33 SYMATTR Value 820k SYMBOL cap 1312 736 M0 SYMATTR InstName C15 SYMATTR Value 1000n SYMBOL cap 1776 768 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C17 SYMATTR Value 1000n SYMBOL res 1360 496 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R35 SYMATTR Value 10k SYMBOL cap 2032 -288 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C18 SYMATTR Value 100n SYMBOL schottky 2272 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D4 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 2272 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R38 SYMATTR Value 470k SYMBOL res 2064 -384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R39 SYMATTR Value 100k SYMBOL schottky 1952 528 M0 SYMATTR Value BAS40HY SYMATTR InstName D10 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1920 704 R0 SYMATTR InstName R41 SYMATTR Value 820k SYMBOL res 2336 464 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R42 SYMATTR Value 100k SYMBOL OpAmps\\LT1058 2128 592 R0 SYMATTR InstName U10 SYMBOL res 2224 640 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R43 SYMATTR Value 820k SYMBOL cap 1904 736 M0 SYMATTR InstName C21 SYMATTR Value 1000n SYMBOL cap 2368 768 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C23 SYMATTR Value 1000n SYMBOL res 1952 496 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R45 SYMATTR Value 10k SYMBOL res 1872 -128 M0 SYMATTR InstName R46 SYMATTR Value 1.5k SYMBOL OpAmps\\LT1058 1408 -192 R0 SYMATTR InstName U7 SYMBOL OpAmps\\LT1058 2000 -192 R0 SYMATTR InstName U9 SYMBOL cap 912 528 R90 WINDOW 0 8 66 VBottom 2 WINDOW 3 -18 -26 VTop 2 SYMATTR InstName C11 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL cap 1504 528 R90 WINDOW 0 6 70 VBottom 2 WINDOW 3 -22 -25 VTop 2 SYMATTR InstName C13 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL cap 2096 528 R90 WINDOW 0 8 70 VBottom 2 WINDOW 3 -19 -25 VTop 2 SYMATTR InstName C14 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL cap -352 -304 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C16 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL res 704 384 R0 SYMATTR InstName R28 SYMATTR Value 560k TEXT -496 136 Left 2 !.tran 0 20 0 1u uic TEXT -496 88 Left 2 !.options plotwinsize=0 numdgt=7 method=trap TEXT -424 -648 Left 2 ;1kHz low distortion sinewave oscillator. TEXT -424 -616 Left 2 ;130dB. Edward Rawde 31 Jan 2025.

It's also way more complex than it need be. Please see my most recent post. I think you'll find the FET is operating conventionally. Roughly at the centre of its range when I last checked.

I've modified the circuit to make sure that FET gate doesn't get forward-biased.

As John May pointed out a long time ago, the J113 isn't a great choice for the application. I've swapped in a J111. The integrator around U6 isn't well designed, and I've deleted a redundant resistor and added a huge damping resistor (R4). It means that there's a lot of 1kHz ripple on the gate voltage, and loads of harmonic content on the output - 2kHz is only 25dB below the fundamental. Getting a low ripple rectified output to feed into the integrator isn't a trivial task. It's part of a negative feedback control problem which you seem to be reluctant to recognise.

Bill Sloman, Sydney

Version 4 SHEET 1 3828 932 WIRE 976 -816 816 -816 WIRE 1056 -816 1056 -848 WIRE 880 -752 880 -768 WIRE 976 -736 976 -816 WIRE 976 -736 912 -736 WIRE 816 -720 816 -816 WIRE 816 -720 720 -720 WIRE 848 -720 816 -720 WIRE 1056 -704 1056 -736 WIRE 1056 -704 912 -704 WIRE 288 -672 256 -672 WIRE 384 -672 352 -672 WIRE 480 -672 464 -672 WIRE 720 -672 720 -720 WIRE 1056 -672 1056 -704 WIRE 1168 -672 1056 -672 WIRE 880 -656 880 -688 WIRE 1056 -656 1056 -672 WIRE 1168 -640 1168 -672 WIRE 1056 -544 1056 -576 WIRE 1168 -544 1168 -576 WIRE 384 -464 384 -480 WIRE 480 -448 480 -672 WIRE 480 -448 416 -448 WIRE 576 -448 480 -448 WIRE 720 -448 720 -592 WIRE 720 -448 576 -448 WIRE 1168 -448 720 -448 WIRE 1664 -448 1168 -448 WIRE 2256 -448 1664 -448 WIRE 256 -432 256 -672 WIRE 352 -432 256 -432 WIRE 448 -416 416 -416 WIRE 464 -416 448 -416 WIRE 576 -400 576 -448 WIRE 1168 -400 1168 -448 WIRE 1664 -384 1664 -448 WIRE 2256 -384 2256 -448 WIRE 384 -368 384 -400 WIRE 1376 -368 1328 -368 WIRE 1520 -368 1456 -368 WIRE 1968 -368 1920 -368 WIRE 2112 -368 2048 -368 WIRE 576 -288 576 -320 WIRE 1168 -288 1168 -320 WIRE 1328 -272 1328 -368 WIRE 1376 -272 1328 -272 WIRE 1520 -272 1520 -368 WIRE 1520 -272 1440 -272 WIRE 1664 -272 1664 -304 WIRE 1920 -272 1920 -368 WIRE 1968 -272 1920 -272 WIRE 2112 -272 2112 -368 WIRE 2112 -272 2032 -272 WIRE 2256 -272 2256 -304 WIRE 256 -240 256 -432 WIRE 976 -192 880 -192 WIRE 1168 -192 1168 -224 WIRE 1168 -192 1040 -192 WIRE 1408 -160 1408 -176 WIRE 2000 -160 2000 -176 WIRE 1328 -144 1328 -272 WIRE 1328 -144 1264 -144 WIRE 1376 -144 1328 -144 WIRE 1920 -144 1920 -272 WIRE 1920 -144 1856 -144 WIRE 1968 -144 1920 -144 WIRE 1520 -128 1520 -272 WIRE 1520 -128 1440 -128 WIRE 1664 -128 1664 -208 WIRE 1664 -128 1520 -128 WIRE 2112 -128 2112 -272 WIRE 2112 -128 2032 -128 WIRE 2256 -128 2256 -208 WIRE 2256 -128 2112 -128 WIRE 1264 -112 1264 -144 WIRE 1376 -112 1328 -112 WIRE 1856 -112 1856 -144 WIRE 1968 -112 1920 -112 WIRE 448 -96 384 -96 WIRE 576 -96 576 -224 WIRE 576 -96 512 -96 WIRE 880 -96 880 -192 WIRE 976 -96 880 -96 WIRE 1168 -96 1168 -192 WIRE 1168 -96 1056 -96 WIRE 160 -80 48 -80 WIRE 208 -80 160 -80 WIRE 256 -80 256 -160 WIRE 256 -80 208 -80 WIRE 1408 -64 1408 -96 WIRE 2000 -64 2000 -96 WIRE 160 -32 160 -80 WIRE 384 0 384 -96 WIRE 448 0 384 0 WIRE 576 0 576 -96 WIRE 576 0 528 0 WIRE 880 0 880 -96 WIRE 928 0 880 0 WIRE 1040 0 1008 0 WIRE 1168 0 1168 -96 WIRE 1168 0 1120 0 WIRE 256 64 256 -80 WIRE 464 96 464 80 WIRE 128 112 112 112 WIRE 160 112 160 48 WIRE 160 112 128 112 WIRE 192 112 160 112 WIRE 304 112 288 112 WIRE 336 112 304 112 WIRE 384 112 384 0 WIRE 384 112 336 112 WIRE 432 112 384 112 WIRE 960 112 960 96 WIRE 576 128 576 0 WIRE 576 128 496 128 WIRE 640 128 576 128 WIRE 672 128 640 128 WIRE 752 128 736 128 WIRE 880 128 880 0 WIRE 880 128 832 128 WIRE 928 128 880 128 WIRE 400 144 384 144 WIRE 432 144 400 144 WIRE 1168 144 1168 0 WIRE 1168 144 992 144 WIRE 1328 144 1328 -112 WIRE 1760 144 1328 144 WIRE 1920 144 1920 -112 WIRE 2352 144 1920 144 WIRE 928 160 880 160 WIRE 112 192 112 112 WIRE 192 192 112 192 WIRE 336 192 336 112 WIRE 336 192 272 192 WIRE 464 192 464 160 WIRE 960 208 960 176 WIRE 640 256 640 128 WIRE 1264 256 1264 -32 WIRE 1264 256 640 256 WIRE 112 288 112 192 WIRE 192 288 112 288 WIRE 464 288 272 288 WIRE 1168 288 1168 144 WIRE 1168 288 464 288 WIRE 1856 288 1856 -32 WIRE 1856 288 1168 288 WIRE 2432 288 1856 288 WIRE 2560 288 2512 288 WIRE 2720 288 2624 288 WIRE 2784 288 2720 288 WIRE -160 336 -160 304 WIRE 880 352 880 160 WIRE 1168 352 880 352 WIRE 1664 352 1664 -128 WIRE 1664 352 1344 352 WIRE 2256 352 2256 -128 WIRE 2256 352 1936 352 WIRE 2784 352 2784 288 WIRE 640 368 640 256 WIRE 720 368 640 368 WIRE 48 384 48 -80 WIRE 240 384 48 384 WIRE 464 400 464 288 WIRE 640 400 640 368 WIRE 720 400 720 368 WIRE 1344 400 1344 352 WIRE 1936 400 1936 352 WIRE -384 432 -384 336 WIRE 240 432 240 384 WIRE -304 448 -304 416 WIRE 2784 448 2784 432 WIRE 48 464 -112 464 WIRE 1024 480 1008 480 WIRE 1056 480 1024 480 WIRE 1168 480 1168 352 WIRE 1168 480 1136 480 WIRE 1600 480 1568 480 WIRE 1648 480 1600 480 WIRE 1760 480 1760 144 WIRE 1760 480 1728 480 WIRE 2192 480 2160 480 WIRE 2240 480 2192 480 WIRE 2352 480 2352 144 WIRE 2352 480 2320 480 WIRE 640 512 640 480 WIRE 720 512 720 480 WIRE 720 512 640 512 WIRE 464 528 464 480 WIRE 640 528 640 512 WIRE 1344 528 1344 480 WIRE 1936 528 1936 480 WIRE -304 544 -304 512 WIRE -48 544 -48 512 WIRE 240 544 240 512 WIRE 848 544 832 544 WIRE 1024 544 912 544 WIRE 1440 544 1424 544 WIRE 1616 544 1504 544 WIRE 2032 544 2016 544 WIRE 2208 544 2096 544 WIRE -112 560 -112 464 WIRE -80 560 -112 560 WIRE 48 576 48 464 WIRE 48 576 -16 576 WIRE 80 576 48 576 WIRE 96 576 80 576 WIRE -160 592 -160 416 WIRE -80 592 -160 592 WIRE -384 608 -384 512 WIRE 944 624 944 592 WIRE 1536 624 1536 592 WIRE 2128 624 2128 592 WIRE -160 640 -160 592 WIRE -160 640 -224 640 WIRE -48 640 -48 608 WIRE 464 640 464 592 WIRE 832 640 832 544 WIRE 832 640 464 640 WIRE 912 640 832 640 WIRE 1344 640 1344 592 WIRE 1424 640 1424 544 WIRE 1424 640 1344 640 WIRE 1504 640 1424 640 WIRE 1936 640 1936 592 WIRE 2016 640 2016 544 WIRE 2016 640 1936 640 WIRE 2096 640 2016 640 WIRE 464 656 464 640 WIRE 464 656 320 656 WIRE 1024 656 1024 544 WIRE 1024 656 976 656 WIRE 1056 656 1024 656 WIRE 1168 656 1168 480 WIRE 1168 656 1136 656 WIRE 1616 656 1616 544 WIRE 1616 656 1568 656 WIRE 1648 656 1616 656 WIRE 1760 656 1760 480 WIRE 1760 656 1728 656 WIRE 2208 656 2208 544 WIRE 2208 656 2160 656 WIRE 2240 656 2208 656 WIRE 2352 656 2352 480 WIRE 2352 656 2320 656 WIRE -160 672 -160 640 WIRE 640 672 640 592 WIRE 912 672 640 672 WIRE 1504 672 1456 672 WIRE 2096 672 2048 672 WIRE -224 688 -224 640 WIRE 464 704 464 656 WIRE 464 704 416 704 WIRE 640 704 640 672 WIRE 640 704 592 704 WIRE 1168 704 1168 656 WIRE 1344 704 1344 640 WIRE 1344 704 1296 704 WIRE 1760 704 1760 656 WIRE 1936 704 1936 640 WIRE 1936 704 1888 704 WIRE 2352 704 2352 656 WIRE 464 720 464 704 WIRE 640 720 640 704 WIRE 944 720 944 688 WIRE 1344 720 1344 704 WIRE 1536 720 1536 688 WIRE 1936 720 1936 704 WIRE 2128 720 2128 688 WIRE 416 736 416 704 WIRE 592 736 592 704 WIRE 1296 736 1296 704 WIRE 1888 736 1888 704 WIRE -224 784 -224 752 WIRE -160 784 -160 752 WIRE 1168 784 1168 768 WIRE 1760 784 1760 768 WIRE 2352 784 2352 768 WIRE 416 832 416 800 WIRE 464 832 464 800 WIRE 464 832 416 832 WIRE 592 832 592 800 WIRE 640 832 640 800 WIRE 640 832 592 832 WIRE 1296 832 1296 800 WIRE 1344 832 1344 800 WIRE 1344 832 1296 832 WIRE 1888 832 1888 800 WIRE 1936 832 1936 800 WIRE 1936 832 1888 832 WIRE 464 864 464 832 WIRE 640 864 640 832 WIRE 1344 864 1344 832 WIRE 1936 864 1936 832 WIRE 320 912 320 656 WIRE 1456 912 1456 672 WIRE 1456 912 320 912 WIRE 2048 912 2048 672 WIRE 2048 912 1456 912 FLAG 384 -480 V+ FLAG 464 80 V+ FLAG 960 96 V+ FLAG 208 -80 gate FLAG 128 112 drn FLAG 2784 448 0 FLAG 2720 288 output FLAG -384 608 0 FLAG 384 -368 0 FLAG 464 192 0 FLAG 960 208 0 FLAG -384 336 V+ FLAG 448 -416 half FLAG 400 144 half FLAG 1024 480 half FLAG -48 640 0 FLAG -48 512 V+ FLAG 80 576 half FLAG -160 784 0 FLAG -160 304 V+ FLAG -224 784 0 FLAG 304 112 src FLAG 880 -768 V+ FLAG 880 -656 0 FLAG 1056 -544 0 FLAG 1056 -848 V+ FLAG 1168 -544 0 FLAG 1168 784 0 FLAG 464 864 0 FLAG 944 592 V+ FLAG 944 720 0 FLAG 1408 -176 V+ FLAG 1408 -64 0 FLAG 1600 480 half FLAG 1760 784 0 FLAG 1344 864 0 FLAG 1536 592 V+ FLAG 1536 720 0 FLAG 2000 -176 V+ FLAG 2000 -64 0 FLAG 2192 480 half FLAG 2352 784 0 FLAG 1936 864 0 FLAG 2128 592 V+ FLAG 2128 720 0 FLAG 640 864 0 FLAG -304 544 0 FLAG -304 416 V+ FLAG 240 544 0 SYMBOL njf 192 64 M90 WINDOW 0 -37 23 VRight 2 WINDOW 3 -9 -3 VRight 2 SYMATTR InstName J1 SYMATTR Value J111 SYMBOL voltage -384 416 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 135 Left 2 WINDOW 0 10 0 Left 2 WINDOW 3 15 104 Left 2 SYMATTR InstName V2 SYMATTR Value 36 SYMBOL schottky 1184 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D2 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 176 176 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 2.2k SYMBOL res 176 -48 M0 WINDOW 0 38 42 Left 2 WINDOW 3 36 66 Left 2 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL res 272 -144 R180 WINDOW 0 40 70 Left 2 WINDOW 3 45 42 Left 2 SYMATTR InstName R1 SYMATTR Value 200k SYMBOL res 1184 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R6 SYMATTR Value 100k SYMBOL cap 352 -688 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 10000n SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM185R60J106ME15" type="X5R" SYMBOL res 1072 -112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R9 SYMATTR Value 15k SYMBOL res 848 112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R12 SYMATTR Value 8.2K SYMBOL cap 1040 -208 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 10n SYMATTR SpiceLine V=16 Irms=647m Rser=0.0322889 Lser=0 mfg="KEMET" pn="C0201C103K4PAC" type="X5R" SYMBOL cap 736 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 22n SYMATTR SpiceLine V=4 Irms=356m Rser=0.150334 Lser=0 mfg="KEMET" pn="C0402C223K7PAC" type="X5R" SYMBOL res 544 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value 10k SYMBOL cap 512 -112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 22p SYMATTR SpiceLine V=16 Irms=0 Rser=0.3482 Lser=551p mfg="W?rth Elektronik" pn="885012006019 WCAP-CSGP 0603" type="NP0" SYMBOL res 704 -688 R0 SYMATTR InstName R17 SYMATTR Value 100k SYMBOL res 2528 272 R90 WINDOW 0 -4 57 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 600 SYMBOL res 2800 448 R180 WINDOW 0 47 75 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R8 SYMATTR Value 600 SYMBOL res -176 432 M180 WINDOW 0 40 70 Left 2 WINDOW 3 37 41 Left 2 SYMATTR InstName R5 SYMATTR Value 100k SYMBOL res -176 768 M180 WINDOW 0 40 70 Left 2 WINDOW 3 38 43 Left 2 SYMATTR InstName R10 SYMATTR Value 100k SYMBOL cap -208 752 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C1 SYMATTR Value 10n SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R" SYMBOL cap 2624 272 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL res 1024 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R11 SYMATTR Value 150k SYMBOL res 288 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R15 SYMATTR Value 7.32k SYMBOL res 1136 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R16 SYMATTR Value 47k SYMBOL OpAmps\\LT1058 -48 512 R0 SYMATTR InstName U5 SYMBOL OpAmps\\LT1058 384 -496 M0 SYMATTR InstName U6 SYMBOL OpAmps\\LT1058 880 -784 M0 WINDOW 0 -79 26 Left 2 WINDOW 3 -120 114 Left 2 SYMATTR InstName U1 SYMBOL res 1040 -832 R0 SYMATTR InstName R19 SYMATTR Value 120k SYMBOL res 1040 -672 R0 SYMATTR InstName R20 SYMATTR Value 100k SYMBOL cap 1152 -576 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C7 SYMATTR Value 10n SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R" SYMBOL OpAmps\\LT1115 464 64 R0 SYMATTR InstName U4 SYMBOL OpAmps\\LT1115 960 80 R0 SYMATTR InstName U3 SYMBOL schottky 592 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D1 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 592 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R18 SYMATTR Value 100k SYMBOL schottky 656 528 M0 SYMATTR Value BAS40HY SYMATTR InstName D5 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 624 704 R0 SYMATTR InstName R21 SYMATTR Value 820k SYMBOL schottky 480 528 M0 SYMATTR Value BAS40HY SYMATTR InstName D6 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 448 704 R0 WINDOW 0 39 28 Left 2 WINDOW 3 41 58 Left 2 SYMATTR InstName R22 SYMATTR Value 820k SYMBOL res 1152 464 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R23 SYMATTR Value 100k SYMBOL OpAmps\\LT1058 944 592 R0 SYMATTR InstName U2 SYMBOL res 1040 640 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R24 SYMATTR Value 820k SYMBOL cap 608 736 M0 WINDOW 0 27 51 Left 2 WINDOW 3 21 77 Left 2 SYMATTR InstName C9 SYMATTR Value 1000n SYMBOL cap 432 736 M0 SYMATTR InstName C10 SYMATTR Value 1000n SYMBOL cap 1184 768 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C8 SYMATTR Value 1000n SYMBOL res 656 496 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R25 SYMATTR Value 10k SYMBOL res 480 496 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R26 SYMATTR Value 10k SYMBOL res 1280 -128 M0 SYMATTR InstName R27 SYMATTR Value 1.5k SYMBOL cap 1440 -288 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C12 SYMATTR Value 100n SYMBOL schottky 1680 -208 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D3 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1680 -288 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R36 SYMATTR Value 100k SYMBOL res 1472 -384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R29 SYMATTR Value 100k SYMBOL schottky 1360 528 M0 SYMATTR Value BAS40HY SYMATTR InstName D8 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1328 704 R0 SYMATTR InstName R31 SYMATTR Value 820k SYMBOL res 1744 464 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R32 SYMATTR Value 100k SYMBOL OpAmps\\LT1058 1536 592 R0 SYMATTR InstName U8 SYMBOL res 1632 640 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R33 SYMATTR Value 820k SYMBOL cap 1312 736 M0 SYMATTR InstName C15 SYMATTR Value 1000n SYMBOL cap 1776 768 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C17 SYMATTR Value 1000n SYMBOL res 1360 496 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R35 SYMATTR Value 10k SYMBOL cap 2032 -288 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C18 SYMATTR Value 100n SYMBOL schottky 2272 -208 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D4 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 2272 -288 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R38 SYMATTR Value 100k SYMBOL res 2064 -384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R39 SYMATTR Value 100k SYMBOL schottky 1952 528 M0 SYMATTR Value BAS40HY SYMATTR InstName D10 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1920 704 R0 SYMATTR InstName R41 SYMATTR Value 820k SYMBOL res 2336 464 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R42 SYMATTR Value 100k SYMBOL OpAmps\\LT1058 2128 592 R0 SYMATTR InstName U10 SYMBOL res 2224 640 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R43 SYMATTR Value 820k SYMBOL cap 1904 736 M0 SYMATTR InstName C21 SYMATTR Value 1000n SYMBOL cap 2368 768 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C23 SYMATTR Value 1000n SYMBOL res 1952 496 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R45 SYMATTR Value 10k SYMBOL res 1872 -128 M0 SYMATTR InstName R46 SYMATTR Value 1.5k SYMBOL OpAmps\\LT1058 1408 -192 R0 SYMATTR InstName U7 SYMBOL OpAmps\\LT1058 2000 -192 R0 SYMATTR InstName U9 SYMBOL cap 912 528 R90 WINDOW 0 8 66 VBottom 2 WINDOW 3 -18 -26 VTop 2 SYMATTR InstName C11 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL cap 1504 528 R90 WINDOW 0 6 70 VBottom 2 WINDOW 3 -22 -25 VTop 2 SYMATTR InstName C13 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL cap 2096 528 R90 WINDOW 0 8 70 VBottom 2 WINDOW 3 -19 -25 VTop 2 SYMATTR InstName C14 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL cap -320 512 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C16 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL res 704 384 R0 SYMATTR InstName R28 SYMATTR Value 560k SYMBOL res 256 528 R180 WINDOW 0 40 70 Left 2 WINDOW 3 45 42 Left 2 SYMATTR InstName R30 SYMATTR Value 200k SYMBOL res 480 -688 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 6800k TEXT -408 -744 Left 2 !.tran 0 20 0 1u uic TEXT -416 -816 Left 2 !.options plotwinsize=0 numdgt=7 method=trap TEXT -424 -648 Left 2 ;1kHz low distortion sinewave oscillator. TEXT -424 -616 Left 2 ;Approaching 130dB. Edward Rawde 30 Jan 2025. TEXT 1352 -640 Left 2 ;As modifed by Bill Sloman 1 Feb 2025, greatly degrading the distortion performance, but fixing some start-up problems.

Why does it matter if the FET gate is forward biased during the first 10ms Bill? That isn't going to make the FET explode is it?

Did he say why?

I've swapped in a J111. The integrator around U6

Sorry bill but I don't get why you would sabotage the circuit like that.

Please see the most recent circuit I posted. It doesn't bother with DC stabilization circuits but it does do 133dB down on harmonics with pretty much nothing at 2kHz at all.

On 1/02/2025 4:37 pm, Edward Rawde wrote:

You aren't a quick study.

Perhaps if you measure the distortion only when the stabilisation circuit isn't feeding anything into the integrator wrapped around U6.

The current feed to set the output level by balancing out the inputs from the rectifiers was feeding in current when it should have been sucking it out, so it wasn't a well thought-out design.

Here's a version of that circuit which does work sensibly, even if the harmonic content of the output is only about 60DB below the fundamental.

-- Bill Sloman, Sydney

Version 4 SHEET 1 3828 932 WIRE 976 -816 816 -816 WIRE 1056 -816 1056 -848 WIRE 880 -752 880 -768 WIRE 976 -736 976 -816 WIRE 976 -736 912 -736 WIRE 816 -720 816 -816 WIRE 816 -720 720 -720 WIRE 848 -720 816 -720 WIRE 1056 -704 1056 -736 WIRE 1056 -704 912 -704 WIRE 288 -672 256 -672 WIRE 384 -672 352 -672 WIRE 480 -672 464 -672 WIRE 720 -672 720 -720 WIRE 1056 -672 1056 -704 WIRE 1168 -672 1056 -672 WIRE 880 -656 880 -688 WIRE 1056 -656 1056 -672 WIRE 1168 -640 1168 -672 WIRE 1056 -544 1056 -576 WIRE 1168 -544 1168 -576 WIRE -192 -480 -192 -512 WIRE 384 -464 384 -480 WIRE 480 -448 480 -672 WIRE 480 -448 416 -448 WIRE 576 -448 480 -448 WIRE 640 -448 576 -448 WIRE 720 -448 720 -592 WIRE 720 -448 640 -448 WIRE 1056 -448 720 -448 WIRE 1168 -448 1056 -448 WIRE 1296 -448 1168 -448 WIRE 1872 -448 1296 -448 WIRE 256 -432 256 -672 WIRE 352 -432 256 -432 WIRE 448 -416 416 -416 WIRE 464 -416 448 -416 WIRE 576 -400 576 -448 WIRE 1056 -400 1056 -448 WIRE 1168 -400 1168 -448 WIRE 1872 -400 1872 -448 WIRE -416 -384 -416 -480 WIRE -336 -368 -336 -400 WIRE 384 -368 384 -400 WIRE 1296 -368 1296 -448 WIRE 1328 -368 1296 -368 WIRE 1424 -368 1408 -368 WIRE 1520 -368 1504 -368 WIRE 16 -352 -144 -352 WIRE 1056 -304 1056 -320 WIRE 1168 -304 1168 -320 WIRE 1168 -304 1056 -304 WIRE 576 -288 576 -320 WIRE 1168 -288 1168 -304 WIRE 1520 -288 1520 -368 WIRE 1872 -288 1872 -320 WIRE -336 -272 -336 -304 WIRE -80 -272 -80 -304 WIRE -144 -256 -144 -352 WIRE -112 -256 -144 -256 WIRE 16 -240 16 -352 WIRE 16 -240 -48 -240 WIRE 48 -240 16 -240 WIRE 64 -240 48 -240 WIRE 256 -240 256 -432 WIRE -192 -224 -192 -400 WIRE -112 -224 -192 -224 WIRE -416 -208 -416 -304 WIRE 976 -192 880 -192 WIRE 1168 -192 1168 -224 WIRE 1168 -192 1040 -192 WIRE -192 -176 -192 -224 WIRE -192 -176 -256 -176 WIRE -80 -176 -80 -208 WIRE -192 -144 -192 -176 WIRE -256 -128 -256 -176 WIRE 1376 -112 1328 -112 WIRE 1520 -112 1520 -224 WIRE 1520 -112 1456 -112 WIRE 448 -96 384 -96 WIRE 576 -96 576 -224 WIRE 576 -96 512 -96 WIRE 880 -96 880 -192 WIRE 976 -96 880 -96 WIRE 1168 -96 1168 -192 WIRE 1168 -96 1056 -96 WIRE 1728 -96 1680 -96 WIRE 1872 -96 1872 -224 WIRE 1872 -96 1808 -96 WIRE 208 -80 160 -80 WIRE 256 -80 256 -160 WIRE 256 -80 208 -80 WIRE -256 -32 -256 -64 WIRE -192 -32 -192 -64 WIRE 160 -32 160 -80 WIRE 1328 -16 1328 -112 WIRE 1376 -16 1328 -16 WIRE 1520 -16 1520 -112 WIRE 1520 -16 1440 -16 WIRE 384 0 384 -96 WIRE 448 0 384 0 WIRE 576 0 576 -96 WIRE 576 0 528 0 WIRE 880 0 880 -96 WIRE 928 0 880 0 WIRE 1040 0 1008 0 WIRE 1168 0 1168 -96 WIRE 1168 0 1120 0 WIRE 1680 0 1680 -96 WIRE 1728 0 1680 0 WIRE 1872 0 1872 -96 WIRE 1872 0 1792 0 WIRE 256 64 256 -80 WIRE 464 96 464 80 WIRE 1408 96 1408 80 WIRE 128 112 112 112 WIRE 160 112 160 48 WIRE 160 112 128 112 WIRE 192 112 160 112 WIRE 304 112 288 112 WIRE 336 112 304 112 WIRE 384 112 384 0 WIRE 384 112 336 112 WIRE 432 112 384 112 WIRE 960 112 960 96 WIRE 1328 112 1328 -16 WIRE 1328 112 1264 112 WIRE 1376 112 1328 112 WIRE 1760 112 1760 96 WIRE 576 128 576 0 WIRE 576 128 496 128 WIRE 640 128 576 128 WIRE 672 128 640 128 WIRE 752 128 736 128 WIRE 880 128 880 0 WIRE 880 128 832 128 WIRE 928 128 880 128 WIRE 1520 128 1520 -16 WIRE 1520 128 1440 128 WIRE 1680 128 1680 0 WIRE 1680 128 1616 128 WIRE 1728 128 1680 128 WIRE 400 144 384 144 WIRE 432 144 400 144 WIRE 1168 144 1168 0 WIRE 1168 144 992 144 WIRE 1344 144 1328 144 WIRE 1376 144 1344 144 WIRE 1872 144 1872 0 WIRE 1872 144 1792 144 WIRE 640 160 640 128 WIRE 896 160 880 160 WIRE 928 160 896 160 WIRE 1264 160 1264 112 WIRE 1696 160 1680 160 WIRE 1728 160 1696 160 WIRE 1616 176 1616 128 WIRE 112 192 112 112 WIRE 192 192 112 192 WIRE 336 192 336 112 WIRE 336 192 272 192 WIRE 464 192 464 160 WIRE 1408 192 1408 160 WIRE 960 208 960 176 WIRE 1760 208 1760 176 WIRE 640 256 640 224 WIRE 1264 256 1264 240 WIRE 1264 256 640 256 WIRE 112 288 112 192 WIRE 192 288 112 288 WIRE 368 288 272 288 WIRE 1168 288 1168 144 WIRE 1168 288 448 288 WIRE 1616 288 1616 256 WIRE 1616 288 1168 288 WIRE 1920 288 1616 288 WIRE 2048 288 2000 288 WIRE 2208 288 2112 288 WIRE 2272 288 2208 288 WIRE 2272 352 2272 288 WIRE 2272 448 2272 432 FLAG 384 -480 V+ FLAG 464 80 V+ FLAG 960 96 V+ FLAG 208 -80 gate FLAG 128 112 drn FLAG 2272 448 0 FLAG 2208 288 output FLAG -416 -208 0 FLAG 384 -368 0 FLAG 464 192 0 FLAG 960 208 0 FLAG -416 -480 V+ FLAG 448 -416 half FLAG 400 144 half FLAG -80 -176 0 FLAG -80 -304 V+ FLAG 48 -240 half FLAG -192 -32 0 FLAG -192 -512 V+ FLAG -256 -32 0 FLAG 304 112 src FLAG 880 -768 V+ FLAG 880 -656 0 FLAG 1056 -544 0 FLAG 1056 -848 V+ FLAG 1168 -544 0 FLAG 1408 80 V+ FLAG 1408 192 0 FLAG 1760 96 V+ FLAG 1760 208 0 FLAG -336 -272 0 FLAG -336 -400 V+ FLAG 640 -448 levelfb FLAG 896 160 half FLAG 1344 144 half FLAG 1696 160 half SYMBOL njf 192 64 M90 WINDOW 0 -37 23 VRight 2 WINDOW 3 -9 -3 VRight 2 SYMATTR InstName J1 SYMATTR Value J111 SYMBOL voltage -416 -400 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 135 Left 2 WINDOW 0 10 0 Left 2 WINDOW 3 15 104 Left 2 SYMATTR InstName V2 SYMATTR Value 36 SYMBOL schottky 1184 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D2 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 176 176 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 2.2k SYMBOL res 176 -48 M0 WINDOW 0 38 42 Left 2 WINDOW 3 36 66 Left 2 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL res 272 -144 R180 WINDOW 0 40 70 Left 2 WINDOW 3 45 42 Left 2 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL res 1184 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R6 SYMATTR Value 470k SYMBOL cap 352 -688 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 1000n SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 SYMBOL res 1072 -112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R9 SYMATTR Value 15k SYMBOL res 848 112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R12 SYMATTR Value 8.2K SYMBOL cap 1040 -208 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 10n SYMATTR SpiceLine V=16 Irms=647m Rser=0.0322889 Lser=0 mfg="KEMET" pn="C0201C103K4PAC" type="X5R" SYMBOL cap 736 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 22n SYMATTR SpiceLine V=4 Irms=356m Rser=0.150334 Lser=0 mfg="KEMET" pn="C0402C223K7PAC" type="X5R" SYMBOL res 544 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value 10k SYMBOL cap 512 -112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 22p SYMATTR SpiceLine V=16 Irms=0 Rser=0.3482 Lser=551p mfg="Würth Elektronik" pn="885012006019 WCAP-CSGP 0603" type="NP0" SYMBOL res 704 -688 R0 SYMATTR InstName R17 SYMATTR Value 470k SYMBOL res 2016 272 R90 WINDOW 0 -4 57 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 600 SYMBOL res 2288 448 R180 WINDOW 0 47 75 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R8 SYMATTR Value 600 SYMBOL res -208 -384 M180 WINDOW 0 40 70 Left 2 WINDOW 3 37 41 Left 2 SYMATTR InstName R5 SYMATTR Value 100k SYMBOL res -208 -48 M180 WINDOW 0 40 70 Left 2 WINDOW 3 38 43 Left 2 SYMATTR InstName R10 SYMATTR Value 100k SYMBOL cap -240 -64 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C1 SYMATTR Value 10n SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R" SYMBOL cap 2112 272 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL res 1024 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R11 SYMATTR Value 150k SYMBOL res 288 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R15 SYMATTR Value 8.2k SYMBOL res 1136 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R16 SYMATTR Value 47k SYMBOL OpAmps\\LT1058 -80 -304 R0 SYMATTR InstName U5 SYMBOL OpAmps\\LT1058 384 -496 M0 SYMATTR InstName U6 SYMBOL OpAmps\\LT1058 880 -784 M0 WINDOW 0 -79 26 Left 2 WINDOW 3 -120 114 Left 2 SYMATTR InstName U1 SYMBOL res 1040 -832 R0 SYMATTR InstName R19 SYMATTR Value 120k SYMBOL res 1040 -672 R0 SYMATTR InstName R20 SYMATTR Value 91k SYMBOL cap 1152 -576 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C7 SYMATTR Value 10n SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R" SYMBOL OpAmps\\LT1115 464 64 R0 SYMATTR InstName U4 SYMBOL OpAmps\\LT1115 960 80 R0 SYMATTR InstName U3 SYMBOL schottky 592 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D1 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 592 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R18 SYMATTR Value 470k SYMBOL res 1280 144 M0 SYMATTR InstName R27 SYMATTR Value 1.5k SYMBOL cap 1440 -32 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C12 SYMATTR Value 100n SYMBOL schottky 1536 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D3 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1408 -352 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R36 SYMATTR Value 470k SYMBOL res 1472 -128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R29 SYMATTR Value 100k SYMBOL cap 1792 -16 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C18 SYMATTR Value 100n SYMBOL schottky 1888 -224 R180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D4 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1888 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R38 SYMATTR Value 470k SYMBOL res 1824 -112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R39 SYMATTR Value 100k SYMBOL res 1632 160 M0 SYMATTR InstName R46 SYMATTR Value 1.5k SYMBOL OpAmps\\LT1058 1408 64 R0 SYMATTR InstName U7 SYMBOL OpAmps\\LT1058 1760 80 R0 SYMATTR InstName U9 SYMBOL cap -352 -304 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C16 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL cap 656 224 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C8 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL res 1424 -384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R22 SYMATTR Value 20k SYMBOL res 1072 -416 M0 SYMATTR InstName R21 SYMATTR Value 7.5Meg SYMBOL res 480 -688 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 220k SYMBOL res 464 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R14 SYMATTR Value 1.1k TEXT -496 136 Left 2 !.tran 0 20 1m 1u uic TEXT -496 88 Left 2 !.options plotwinsize=0 numdgt=7 method=trap TEXT -440 -824 Left 2 ;1kHz low distortion sinewave oscillator. TEXT -440 -792 Left 2 ;133dB. Edward Rawde 1 Feb 2025. TEXT -432 -760 Left 2 ;Modified by Bill Sloman 1 Feb 2025. R19 and R20 have been swapped. TEXT -432 -728 Left 2 ;Distortion is higher, but start-up works better.

"Bill Sloman" snipped-for-privacy@ieee.org wrote in message news:vnl3gl$30im$ snipped-for-privacy@dont-email.me...

But that's completely nuts Bill. If I really do want 1kHz with -133dB harmonic distortion in reality then I'm prepared to wait 20 seconds for it. In fact I'm prepared to wait a minute or two if that's what it takes for the harmonic distortion to go down to -133dB.

If there's a problem with the design around U6 then why doesn't that also apply to U7 and U9?

It's not intended as a volume production design. I might make two or three boards and test it. But I don't have equipment capable of measuring -133dB harmonic distortion.

I would also be prepared to make adjustments to the circuit for minimum distortion. This circuit might have up to six adjustments if built for real so it can be adjusted for correct output level and minimum distortion.

The circuit included below might be my final offering on this matter. There's nothing visible at 2kHz and 3kHz is barely visible. It requires only a cheap quad op amp package in addition to the two LT1115 devices.

If you can show me a circuit which has -133dB harmonic distortion and also faster settling time then I'd like to see it but if you're going to insist that it has to have only -60 dB harmonic distortion performance (which interestingly is about that of your own circuit) just because the settling time can be made shorter then I'm sorry but all that's going to do is make me wonder about your mental health.

If you believe that a real version of the circuit below could not be adjusted to better than -130dB (with suitable test equipment) then please let me know. It might take an hour to complete the adjustments but that's ok with me because as previously stated it's not intended as a production design which just works after assembly.

It takes my computer about 10 minutes (LTSpice 24.1.1) to complete 20 seconds of simulation for the following circuit. I usually watch the output and the current in each of the four diodes.

When it's done, take a sample of the output near 20s and FFT with Blackman-Harris window.

Version 4.1 SHEET 1 3828 932 WIRE 832 -768 832 -800 WIRE 336 -672 256 -672 WIRE 480 -672 400 -672 WIRE 832 -656 832 -688 WIRE 832 -656 720 -656 WIRE 832 -624 832 -656 WIRE 944 -624 832 -624 WIRE 720 -608 720 -656 WIRE 832 -608 832 -624 WIRE 944 -592 944 -624 WIRE 256 -576 256 -672 WIRE 336 -576 256 -576 WIRE 480 -576 480 -672 WIRE 480 -576 416 -576 WIRE 832 -496 832 -528 WIRE 944 -496 944 -528 WIRE -192 -480 -192 -512 WIRE 384 -464 384 -480 WIRE 480 -448 480 -576 WIRE 480 -448 416 -448 WIRE 576 -448 480 -448 WIRE 640 -448 576 -448 WIRE 720 -448 720 -528 WIRE 720 -448 640 -448 WIRE 1056 -448 720 -448 WIRE 1168 -448 1056 -448 WIRE 1296 -448 1168 -448 WIRE 1872 -448 1296 -448 WIRE 256 -432 256 -576 WIRE 352 -432 256 -432 WIRE 448 -416 416 -416 WIRE 464 -416 448 -416 WIRE 576 -400 576 -448 WIRE 1056 -400 1056 -448 WIRE 1168 -400 1168 -448 WIRE 1872 -400 1872 -448 WIRE -416 -384 -416 -480 WIRE -336 -368 -336 -400 WIRE 384 -368 384 -400 WIRE 1296 -368 1296 -448 WIRE 1328 -368 1296 -368 WIRE 1424 -368 1408 -368 WIRE 1520 -368 1504 -368 WIRE 16 -352 -144 -352 WIRE 1056 -304 1056 -320 WIRE 1168 -304 1168 -320 WIRE 1168 -304 1056 -304 WIRE 576 -288 576 -320 WIRE 1168 -288 1168 -304 WIRE 1520 -288 1520 -368 WIRE 1872 -288 1872 -320 WIRE -336 -272 -336 -304 WIRE -80 -272 -80 -304 WIRE -144 -256 -144 -352 WIRE -112 -256 -144 -256 WIRE 16 -240 16 -352 WIRE 16 -240 -48 -240 WIRE 48 -240 16 -240 WIRE 64 -240 48 -240 WIRE 256 -240 256 -432 WIRE -192 -224 -192 -400 WIRE -112 -224 -192 -224 WIRE -416 -208 -416 -304 WIRE 976 -192 880 -192 WIRE 1168 -192 1168 -224 WIRE 1168 -192 1040 -192 WIRE 1376 -192 1328 -192 WIRE 1520 -192 1520 -224 WIRE 1520 -192 1456 -192 WIRE 1728 -192 1680 -192 WIRE 1872 -192 1872 -224 WIRE 1872 -192 1808 -192 WIRE -192 -176 -192 -224 WIRE -192 -176 -256 -176 WIRE -80 -176 -80 -208 WIRE -192 -144 -192 -176 WIRE -256 -128 -256 -176 WIRE 448 -96 384 -96 WIRE 576 -96 576 -224 WIRE 576 -96 512 -96 WIRE 880 -96 880 -192 WIRE 976 -96 880 -96 WIRE 1168 -96 1168 -192 WIRE 1168 -96 1056 -96 WIRE 1328 -96 1328 -192 WIRE 1376 -96 1328 -96 WIRE 1520 -96 1520 -192 WIRE 1520 -96 1440 -96 WIRE 1680 -96 1680 -192 WIRE 1728 -96 1680 -96 WIRE 1872 -96 1872 -192 WIRE 1872 -96 1792 -96 WIRE 208 -80 160 -80 WIRE 256 -80 256 -160 WIRE 256 -80 208 -80 WIRE -256 -32 -256 -64 WIRE -192 -32 -192 -64 WIRE 160 -32 160 -80 WIRE 384 0 384 -96 WIRE 448 0 384 0 WIRE 576 0 576 -96 WIRE 576 0 528 0 WIRE 880 0 880 -96 WIRE 928 0 880 0 WIRE 1040 0 1008 0 WIRE 1168 0 1168 -96 WIRE 1168 0 1120 0 WIRE 1408 16 1408 0 WIRE 1760 16 1760 0 WIRE 1328 32 1328 -96 WIRE 1328 32 1264 32 WIRE 1376 32 1328 32 WIRE 1680 32 1680 -96 WIRE 1680 32 1616 32 WIRE 1728 32 1680 32 WIRE 1264 48 1264 32 WIRE 1520 48 1520 -96 WIRE 1520 48 1440 48 WIRE 1616 48 1616 32 WIRE 1872 48 1872 -96 WIRE 1872 48 1792 48 WIRE 256 64 256 -80 WIRE 1344 64 1328 64 WIRE 1376 64 1344 64 WIRE 1696 64 1680 64 WIRE 1728 64 1696 64 WIRE 464 96 464 80 WIRE 128 112 112 112 WIRE 160 112 160 48 WIRE 160 112 128 112 WIRE 192 112 160 112 WIRE 304 112 288 112 WIRE 336 112 304 112 WIRE 384 112 384 0 WIRE 384 112 336 112 WIRE 432 112 384 112 WIRE 960 112 960 96 WIRE 1408 112 1408 80 WIRE 1760 112 1760 80 WIRE 576 128 576 0 WIRE 576 128 496 128 WIRE 640 128 576 128 WIRE 672 128 640 128 WIRE 752 128 736 128 WIRE 880 128 880 0 WIRE 880 128 832 128 WIRE 928 128 880 128 WIRE 400 144 384 144 WIRE 432 144 400 144 WIRE 1168 144 1168 0 WIRE 1168 144 992 144 WIRE 896 160 880 160 WIRE 928 160 896 160 WIRE 1264 160 1264 128 WIRE 1616 160 1616 128 WIRE 112 192 112 112 WIRE 192 192 112 192 WIRE 336 192 336 112 WIRE 336 192 272 192 WIRE 464 192 464 160 WIRE 960 208 960 176 WIRE 640 256 640 128 WIRE 1264 256 1264 224 WIRE 1264 256 640 256 WIRE 112 320 112 192 WIRE 192 320 112 320 WIRE 336 320 272 320 WIRE 1168 320 1168 144 WIRE 1168 320 416 320 WIRE 1616 320 1616 224 WIRE 1616 320 1168 320 WIRE 1712 320 1616 320 WIRE 1840 320 1792 320 WIRE 2000 320 1904 320 WIRE 2064 320 2000 320 WIRE 2064 384 2064 320 WIRE 2064 480 2064 464 FLAG 384 -480 V+ FLAG 464 80 V+ FLAG 960 96 V+ FLAG 208 -80 gate FLAG 128 112 drn FLAG 2064 480 0 FLAG 2000 320 output FLAG -416 -208 0 FLAG 384 -368 0 FLAG 464 192 0 FLAG 960 208 0 FLAG -416 -480 V+ FLAG 448 -416 half FLAG 400 144 half FLAG -80 -176 0 FLAG -80 -304 V+ FLAG 48 -240 half FLAG -192 -32 0 FLAG -192 -512 V+ FLAG -256 -32 0 FLAG 304 112 src FLAG 832 -496 0 FLAG 832 -800 V+ FLAG 944 -496 0 FLAG 1408 0 V+ FLAG 1408 112 0 FLAG 1760 0 V+ FLAG 1760 112 0 FLAG -336 -272 0 FLAG -336 -400 V+ FLAG 640 -448 levelfb FLAG 896 160 half FLAG 1344 64 half FLAG 1696 64 half SYMBOL njf 192 64 M90 WINDOW 0 -37 23 VRight 2 WINDOW 3 -9 -3 VRight 2 SYMATTR InstName J1 SYMATTR Value J113 SYMBOL voltage -416 -400 R0 WINDOW 123 0 0 Left 0 WINDOW 39 10 135 Left 2 WINDOW 0 10 0 Left 2 WINDOW 3 15 104 Left 2 SYMATTR InstName V2 SYMATTR Value 36 SYMBOL schottky 1152 -224 M180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D2 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 176 176 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 22 SYMBOL res 176 -48 M0 WINDOW 0 38 42 Left 2 WINDOW 3 36 66 Left 2 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL res 272 -144 R180 WINDOW 0 40 70 Left 2 WINDOW 3 45 42 Left 2 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL res 320 -560 R270 WINDOW 0 33 55 VTop 2 WINDOW 3 -3 55 VBottom 2 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL res 1184 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R6 SYMATTR Value 470k SYMBOL cap 400 -688 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 10000n SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM185R60J106ME15" type="X5R" SYMBOL res 1072 -112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R9 SYMATTR Value 15k SYMBOL res 848 112 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R12 SYMATTR Value 8.2K SYMBOL cap 1040 -208 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 10n SYMATTR SpiceLine V=16 Irms=647m Rser=0.0322889 Lser=0 mfg="KEMET" pn="C0201C103K4PAC" type="X5R" SYMBOL cap 736 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 22n SYMATTR SpiceLine V=4 Irms=356m Rser=0.150334 Lser=0 mfg="KEMET" pn="C0402C223K7PAC" type="X5R" SYMBOL res 544 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value 10k SYMBOL cap 512 -112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 22p SYMATTR SpiceLine V=16 Irms=0 Rser=0.3482 Lser=551p mfg="Würth Elektronik" pn="885012006019 WCAP-CSGP 0603" type="NP0" SYMBOL res 432 304 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R14 SYMATTR Value 1371 SYMBOL res 704 -624 R0 SYMATTR InstName R17 SYMATTR Value 430k SYMBOL res 1808 304 R90 WINDOW 0 -4 57 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 600 SYMBOL res 2080 480 R180 WINDOW 0 47 75 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R8 SYMATTR Value 600 SYMBOL res -208 -384 M180 WINDOW 0 40 70 Left 2 WINDOW 3 37 41 Left 2 SYMATTR InstName R5 SYMATTR Value 100k SYMBOL res -208 -48 M180 WINDOW 0 40 70 Left 2 WINDOW 3 38 43 Left 2 SYMATTR InstName R10 SYMATTR Value 100k SYMBOL cap -240 -64 R180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C1 SYMATTR Value 10n SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R" SYMBOL cap 1904 304 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL res 1024 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R11 SYMATTR Value 150k SYMBOL res 288 304 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R15 SYMATTR Value 8.2k SYMBOL res 1136 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R16 SYMATTR Value 47k SYMBOL OpAmps\\LT1058 -80 -304 R0 SYMATTR InstName U5 SYMBOL OpAmps\\LT1058 384 -496 M0 SYMATTR InstName U6 SYMBOL res 816 -784 R0 SYMATTR InstName R19 SYMATTR Value 91k SYMBOL res 816 -624 R0 SYMATTR InstName R20 SYMATTR Value 120k SYMBOL cap 928 -528 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C7 SYMATTR Value 10n SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R" SYMBOL OpAmps\\LT1115 464 64 R0 SYMATTR InstName U4 SYMBOL OpAmps\\LT1115 960 80 R0 SYMATTR InstName U3 SYMBOL schottky 560 -224 M180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D1 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 592 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R18 SYMATTR Value 470k SYMBOL res 1280 32 M0 SYMATTR InstName R27 SYMATTR Value 1.5k SYMBOL cap 1440 -112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C12 SYMATTR Value 100n SYMBOL schottky 1504 -224 M180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D3 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1408 -352 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R36 SYMATTR Value 470k SYMBOL res 1472 -208 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R29 SYMATTR Value 100k SYMBOL cap 1792 -112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C18 SYMATTR Value 100n SYMBOL schottky 1856 -224 M180 WINDOW 3 24 0 Left 2 WINDOW 0 24 64 Left 2 SYMATTR Value BAS40HY SYMATTR InstName D4 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 1888 -304 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R38 SYMATTR Value 470k SYMBOL res 1824 -208 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R39 SYMATTR Value 100k SYMBOL res 1632 32 M0 SYMATTR InstName R46 SYMATTR Value 1.5k SYMBOL OpAmps\\LT1058 1408 -16 R0 SYMATTR InstName U7 SYMBOL OpAmps\\LT1058 1760 -16 R0 SYMATTR InstName U9 SYMBOL cap -352 -304 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C16 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL cap 1248 224 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C8 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" SYMBOL res 1424 -384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R22 SYMATTR Value 20k SYMBOL res 1072 -416 M0 SYMATTR InstName R21 SYMATTR Value 7.5Meg SYMBOL cap 1600 224 M180 WINDOW 0 24 56 Left 2 WINDOW 3 24 8 Left 2 SYMATTR InstName C9 SYMATTR Value 10000n SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R" TEXT -496 136 Left 2 !.tran 0 20 1m 1u uic TEXT -496 88 Left 2 !.options plotwinsize=0 numdgt=7 method=trap TEXT -424 -648 Left 2 ;1kHz low distortion sinewave oscillator. TEXT -424 -616 Left 2 ;133dB. Edward Rawde 31 Jan 2025.

I you're using polyphase sampling you may as well use a svo. The LT115 is not a good choice - it's phase margin is close to zero and it is liable to sing at about 25MHz.

Version 4 SHEET 1 3020 1316 WIRE 432 -160 64 -160 WIRE 1152 -160 512 -160 WIRE 64 -48 64 -160 WIRE 432 -48 64 -48 WIRE 752 -48 512 -48 WIRE 64 32 64 -48 WIRE 176 32 64 32 WIRE 320 32 256 32 WIRE 608 32 560 32 WIRE 752 32 752 -48 WIRE 752 32 672 32 WIRE 1008 32 960 32 WIRE 1152 32 1152 -160 WIRE 1152 32 1072 32 WIRE 64 144 64 32 WIRE 176 144 64 144 WIRE 320 144 320 32 WIRE 432 144 320 144 WIRE 560 144 560 32 WIRE 560 144 512 144 WIRE 608 144 560 144 WIRE 752 144 752 32 WIRE 832 144 752 144 WIRE 960 144 960 32 WIRE 960 144 912 144 WIRE 1008 144 960 144 WIRE 320 160 320 144 WIRE 320 160 240 160 WIRE 752 160 752 144 WIRE 752 160 672 160 WIRE 1152 160 1152 32 WIRE 1152 160 1072 160 WIRE 1184 160 1152 160 WIRE 176 176 64 176 WIRE 608 176 576 176 WIRE 1008 176 976 176 WIRE 576 208 576 176 WIRE 976 208 976 176 WIRE 64 288 64 176 WIRE 160 288 64 288 WIRE 560 288 240 288 WIRE 752 288 752 160 WIRE 752 288 560 288 WIRE 752 336 752 288 WIRE -224 400 -224 384 WIRE -224 400 -288 400 WIRE -288 416 -288 400 WIRE -224 416 -224 400 WIRE 64 432 64 288 WIRE 752 448 752 416 WIRE 864 448 752 448 WIRE 720 464 688 464 WIRE 720 496 720 464 WIRE 752 496 752 448 WIRE 864 496 864 448 WIRE 736 608 736 560 WIRE 864 608 864 576 WIRE 864 608 736 608 WIRE 320 656 320 160 WIRE 560 656 560 288 WIRE 736 656 736 608 WIRE 1152 656 1152 160 WIRE 64 688 64 512 WIRE -320 752 -400 752 WIRE -176 752 -256 752 WIRE 320 752 320 720 WIRE 560 752 560 720 WIRE 736 752 736 720 WIRE 1152 752 1152 720 WIRE -400 848 -400 752 WIRE -320 848 -400 848 WIRE -176 848 -176 752 WIRE -176 848 -256 848 WIRE 320 880 320 832 WIRE 560 880 560 832 WIRE 560 880 320 880 WIRE 736 880 736 832 WIRE 736 880 560 880 WIRE 1152 880 1152 832 WIRE 1152 880 736 880 WIRE 64 912 64 768 WIRE 64 912 -16 912 WIRE -400 928 -400 848 WIRE -384 928 -400 928 WIRE -288 928 -304 928 WIRE -176 928 -176 848 WIRE -176 928 -224 928 WIRE -16 944 -16 912 WIRE 320 976 320 880 WIRE 64 992 64 912 WIRE -176 1008 -176 928 WIRE -400 1040 -400 928 WIRE -320 1040 -400 1040 WIRE -176 1056 -176 1008 WIRE -176 1056 -256 1056 WIRE -144 1056 -176 1056 WIRE -16 1056 -16 1024 WIRE -16 1056 -64 1056 WIRE 16 1056 -16 1056 WIRE -320 1072 -352 1072 WIRE -352 1120 -352 1072 WIRE -400 1184 -400 1040 WIRE 320 1184 320 1056 WIRE 320 1184 -400 1184 WIRE 400 1184 320 1184 WIRE 528 1184 480 1184 FLAG 576 208 0 FLAG 976 208 0 FLAG -288 416 0 FLAG -224 304 vcc FLAG -224 496 vee FLAG 1184 160 vout FLAG 64 1088 0 FLAG -288 1024 vcc FLAG -288 1088 vee FLAG -352 1120 0 FLAG 688 464 0 FLAG 592 1184 vee FLAG -176 1008 vx SYMBOL res 272 16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 10K SYMBOL res 528 128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 16K SYMBOL res 928 128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 16K SYMBOL cap 672 16 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 10n SYMBOL cap 1072 16 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 10n SYMBOL res 528 -176 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 10K SYMBOL res 528 -64 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R5 SYMATTR Value 82k SYMBOL res 256 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 10K SYMBOL res 48 416 R0 SYMATTR InstName R7 SYMATTR Value 470 SYMBOL voltage -224 288 R0 SYMATTR InstName V1 SYMATTR Value 15 SYMBOL voltage -224 400 R0 SYMATTR InstName V2 SYMATTR Value 15 SYMBOL njf 16 992 R0 SYMATTR InstName J1 SYMATTR Value 2N4391 SYMBOL res -160 1040 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R8 SYMATTR Value 100k SYMBOL res 0 1040 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R9 SYMATTR Value 100k SYMBOL cap -320 832 M90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 1u SYMBOL res 384 1200 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R10 SYMATTR Value 330K SYMBOL diode 528 1200 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D1 SYMATTR Value 1N914 SYMBOL res 304 960 R0 SYMATTR InstName R11 SYMATTR Value 47K SYMBOL OpAmps\\LT1679 -288 1056 R0 SYMATTR InstName U7 SYMBOL cap -288 912 M90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 10U SYMBOL res -400 912 M90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R12 SYMATTR Value 10K SYMBOL diode -256 768 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D3 SYMATTR Value 1N914 SYMBOL res 880 592 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R18 SYMATTR Value 10K SYMBOL res 768 432 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R19 SYMATTR Value 10k SYMBOL diode 336 656 M0 SYMATTR InstName D2 SYMATTR Value 1N914 SYMBOL diode 576 656 M0 SYMATTR InstName D12 SYMATTR Value 1N914 SYMBOL diode 720 656 R0 SYMATTR InstName D13 SYMATTR Value 1N914 SYMBOL diode 1168 656 M0 SYMATTR InstName D14 SYMATTR Value 1N914 SYMBOL res 80 672 M0 SYMATTR InstName R29 SYMATTR Value 95 SYMBOL OpAmps\\opamp 208 96 R0 SYMATTR InstName U5 SYMATTR SpiceLine Aol=5Meg SYMATTR SpiceLine2 GBW=60Meg SYMBOL OpAmps\\opamp 640 96 R0 SYMATTR InstName U6 SYMATTR SpiceLine Aol=5Meg SYMATTR SpiceLine2 GBW=60Meg SYMBOL OpAmps\\opamp 1040 96 R0 SYMATTR InstName U8 SYMATTR SpiceLine Aol=5Meg SYMATTR SpiceLine2 GBW=60Meg SYMBOL res 304 736 R0 SYMATTR InstName R13 SYMATTR Value 68k SYMBOL res 544 736 R0 SYMATTR InstName R14 SYMATTR Value 68k SYMBOL res 752 736 M0 SYMATTR InstName R15 SYMATTR Value 68k SYMBOL res 1136 736 R0 SYMATTR InstName R16 SYMATTR Value 68k SYMBOL OpAmps\\opamp 800 528 R90 SYMATTR InstName U1 SYMATTR SpiceLine Aol=5Meg SYMATTR SpiceLine2 GBW=60Meg TEXT -408 40 Left 2 !.ic v(vp3)=5 V(VG)=-6.8 TEXT -408 72 Left 2 !.tran 0 10 0 1u uic TEXT -408 8 Left 2 !.options plotwinsize=0 numdgt=7 TEXT -408 104 Left 2 !.lib opamp.sub TEXT -408 136 Left 2 !.ic v(vout)=2 v(vx)=-4

Very interesting circuit. Thank you.

Is there a suitable available alternative to LT1115? I have seen LT1115 oscillate at 24 MHz in LTSpice 24.1.1 It doesn't seem to always happen and when it does a little extra load on the output seems to get rid of it.

You don't seem to be able to follow the logic. In fact the 220k damping resistor at R4 was too with a 1uF integrating capacitor at C3 and reducing to 33k gave a very slightly under-damped response, and dropped the harmonis to about 75dB below the fundamental.

But somebody actually using the circuit would want the distortion to be equally low at 40 seconds and later,

But don't seem to appreciate the risk that it might start going up again.

They are acting as phase shifters, not integrators

Get a 20b-bit A/D converter chip that is faster enough for audio, damp a few second of it's output into a memory chip and run a Fourier transform on that data.

Wonder all you like. You psychoanalytic skills seem to be on par with your circuit design skills.

I don't have any strong opinion on the subject, but I wouldn't spend money to find out.

There are better approaches.

I'll pass.

...

If your circuit design skills are demonstrated by a circuit which uses 93 components (which includes 9 transistors and 10 integrated circuits) and only gets 60dB down on harmonics then I agree that pass is for the best.

If you think that circuit design skills can be assessed by counting components, we can draw our own conclusions.

Stop making me laugh please Bill. Who is "we" anyway. You sound like you speak for everyone here.

Element 14 says that the J111 is cheap and it has 14000 available globally.

It's fairly close to the 2N4319 in terms of gate cut-off voltage - much closer than the J113.

You first.

Scarcely everybody. Cursitor Doom posts here regularly and is well aware that he lacks any design skills, or the skills to assess them.

And so is Bill! Sadly, Bill stopped making useful contributions to this group many years ago and now spends his days attempting to appear superior to everyone else.

Of course. Nothing unreasonable about that.

Many of us here have been wondering about Bill's mental health for the past 2 decades. Please try to remember you're dealing with SED's biggest troll here (and he hasn't been fed well lately).

If you are unemployable and never build what you simulate, more parts are no problem.

That's the Royal We.

If you actually build one, how would you measure the distortion?

(I can think of one way)

I'd expect it to be worse than the sim, even ignoring noise.

There is a hobby of playing with LT Spice as a sort of video game, never building or even needing the circuit. Nothing wrong with that I guess, except that the pay isn't very good.

I didn't insist on anything. I debugged Edward's simulation to the point where it started up properly and settled down to a stable state fairly quickly, and reported that the changes that I'd made had upped the harmonic content. After I'd found another bug in his design I finally got the harmonic content closer to about 75dB below the fundamental.

My current mirror variation is stuck at a -60dB. Posting it here didn't get me any helpful suggestions about making it better.

Cursitor Doom - who actually is an anonymous troll - does like to claim that people who object to his habit of posting fatuous nonsense aren't to be taken seriously. One can understand why - it's just one more tranche of fatuous nonsense, and he gets some kind of bizarre satisfaction from posting all sorts of different kinds of utter nonsense.

I really shouldn't go to the trouble of objecting one more example of his malicious fantasising, but I do find it irritating when he starts sticking his oar into serious discussions.