Yes, though if I wanted the wrong answer quickly I could easily make my own ideal amplifier model. The transistor level models converge more reliably too, in my experience. I have often had to modify vendor models to stop them from preventing convergence or causing timestep too small problems - that was a real waste of time. Simulation time is usually not a problem these days, but if it were, then they could provide two models, which they already have anyway.
I generally use the LT Spice UniversalOpamp2 model, and tweak the parameters if needed.
-- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
On Wednesday, September 2, 2020 at 1:45:41 AM UTC+10, snipped-for-privacy@gmail.com wrot e:
right direction.
at I need to lengthen to 25nS. I have built many oneshot/timer circuits ove r the years but never this fast. My research seems to indicate that most ti mers (available ICs) need a minimum trigger pulse of several to ~ hundred n S. Retrigger time doesn't seem to be an issue (yet).
This circuit seems to do the job. R2 and R7 would be realised as a potentio meter - padded at both ends - which you would use to twiddle the quiescent voltage at the base of Q2 to be at the half maximum of the pulse you wanted to stretch. If the incoming pulse has an uncertain height, you'd make the threshold a bit lower, and live with the fact that bigger pulses trigger e arly, or go on to realise a constant fraction discriminator, which is quite a bit more demanding, but perfectly practical with modern comparators (tho ugh it wasn't - quite - back in 1979).
R13 and R5 present a relatively low - but resistive - impedance at the base of Q2 which should be enough to stop the BFR92 from going into oscillation , which they have been known to do.
Version 4 SHEET 1 2924 1040 WIRE -592 -720 -768 -720 WIRE 128 -720 -592 -720 WIRE 304 -720 128 -720 WIRE 768 -720 304 -720 WIRE 976 -720 768 -720 WIRE 1488 -576 1488 -720 WIRE 128 -560 128 -720 WIRE 304 -560 304 -720 WIRE 768 -560 768 -720 WIRE -592 -384 -592 -720 WIRE 1072 -368 1072 -400 WIRE 768 -320 768 -480 WIRE 960 -320 768 -320 WIRE 1008 -320 960 -320 WIRE 128 -288 128 -480 WIRE 176 -288 128 -288 WIRE 576 -288 240 -288 WIRE 768 -208 768 -320 WIRE 304 -160 304 -480 WIRE 400 -160 304 -160 WIRE 576 -160 576 -288 WIRE 576 -160 480 -160 WIRE 640 -160 576 -160 WIRE 704 -160 640 -160 WIRE -768 -64 -768 -720 WIRE 128 48 128 -288 WIRE -272 96 -432 96 WIRE 64 96 -192 96 WIRE 640 128 640 -160 WIRE 304 160 304 -160 WIRE -432 240 -432 96 WIRE -768 416 -768 16 WIRE -768 416 -880 416 WIRE -736 416 -768 416 WIRE -592 416 -592 -320 WIRE -592 416 -736 416 WIRE -496 416 -592 416 WIRE -432 416 -432 320 WIRE -432 416 -496 416 WIRE 640 416 640 208 WIRE 640 416 -432 416 WIRE 1072 416 640 416 WIRE 128 464 128 144 WIRE 768 464 768 -112 WIRE 768 464 128 464 WIRE -880 496 -880 416 WIRE 768 496 768 464 WIRE -736 640 -736 416 WIRE -496 640 -496 416 WIRE -736 656 -736 640 WIRE -736 944 -736 720 WIRE -496 944 -496 704 WIRE -496 944 -736 944 WIRE 304 944 304 240 WIRE 304 944 -496 944 WIRE 768 944 768 576 WIRE 768 944 304 944 WIRE 1760 944 768 944 FLAG -880 496 0 FLAG 960 -320 out SYMBOL npn 64 48 R0 SYMATTR InstName Q1 SYMATTR Value BFR92A SYMBOL npn 704 -208 R0 SYMATTR InstName Q2 SYMATTR Value BFR92A SYMBOL voltage -768 -80 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 44 Left 2 SYMATTR SpiceLine Rser=0.1 SYMATTR InstName V1 SYMATTR Value 5.0 SYMBOL voltage -736 624 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 44 Left 2 SYMATTR SpiceLine Rser=0.1 SYMATTR InstName V2 SYMATTR Value 4.5 SYMBOL voltage -432 224 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value PULSE(0 0.2 1n 300p 300p 100p 200n 2) SYMBOL res -176 80 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 27 SYMBOL res 752 480 R0 SYMATTR InstName R3 SYMATTR Value 750 SYMBOL res 112 -576 R0 SYMATTR InstName R4 SYMATTR Value 390 SYMBOL res 624 112 R0 SYMATTR InstName R5 SYMATTR Value 100 SYMBOL res 752 -576 R0 SYMATTR InstName R6 SYMATTR Value 390 SYMBOL res 288 -576 R0 SYMATTR InstName R2 SYMATTR Value 1k SYMBOL cap 240 -304 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 82p SYMBOL res 288 144 R0 SYMATTR InstName R7 SYMATTR Value 1k2 SYMBOL res 496 -176 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value 100 SYMBOL cap -608 -384 R0 SYMATTR InstName C3 SYMATTR Value 10n SYMBOL cap -512 640 R0 SYMATTR InstName C4 SYMATTR Value 10n TEXT -272 1000 Left 2 !.model BFR92A NPN(IS=0.1213E-15 VAF=30 BF=94.7
3 IKF=0.46227 XTB=0 BR=10.729 CJC=946.47E-15 CJE=10.416E-15 TR =1.2744E-9 TF=26.796E-12 ITF=0.0044601 VTF=0.32861 XTF=0.3817 R B=14.998 RC=0.13793 RE=0.29088 Vceo=15 Icrating=4m mfg=Infineon ) TEXT -904 1024 Left 2 !.tran 0 500n 0-- Bill Sloman, Sydney
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