LM386 minimum count circuit

Christopher Howard · 2025-12-08T16:07:22+00:00

Hi, I had some LM386 chips on hand, and I downloaded the LM386 LowVoltage Audio Power Amplifier data sheet (Rev C). built, on a breadboard, the minimum part count application on page 8(Figure 10, section 9.2.1), except that I got rid of the 10k volumecontrol resistor on pin 3, and I replaced the speaker with a 4 ohmresistor. Am using a 6V supply for pin 6, and feeding in test signals ofabout 5 kHz, amplitude 100 mV RMS.I'm finding, though, that — unless I ground out the input — that howeverI tweak the input frequency or amplitude, I still get garbage output.The output looks like some kind of complicated sum of many saturatedsignals of various frequencies.Does anybody have thoughts on where I might have gone wrong, to guide mytroubleshooting?I re-checked my pin connections a few times, and the component values,which are reasonably close. I replaced the LM386 chip once as well, andgot the same results.

E

Edward Rawde 7 months ago

"Christopher Howard" snipped-for-privacy@librehacker.com wrote in message news: snipped-for-privacy@librehacker.com...

LM386 is designed as a low count component amplifier not a general purpose op amp.

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If I wanted to use any 47uF capacitors I'd put one from pin 6 to ground and one from pin 7 to ground.

No other components are required except perhaps capacitors to remove DC depending on your signal source and what you want to connect the output to.

With a 9V supply the output should be sitting at roughly half of that.

With 100mV signal in you should see a voltage gain of 20.

See the schematic below.

Version 4.1 SHEET 1 880 1096 WIRE -1472 -64 -1568 -64 WIRE -752 -64 -1472 -64 WIRE 160 -64 -752 -64 WIRE 336 -64 160 -64 WIRE 512 -64 336 -64 WIRE 560 -64 512 -64 WIRE 576 -64 560 -64 WIRE 160 -32 160 -64 WIRE -752 0 -752 -64 WIRE 336 0 336 -64 WIRE -1472 16 -1472 -64 WIRE 160 80 160 32 WIRE -800 128 -928 128 WIRE -752 128 -752 80 WIRE -752 128 -800 128 WIRE -1472 144 -1472 80 WIRE 336 144 336 80 WIRE -752 176 -752 128 WIRE -928 192 -928 128 WIRE 160 192 160 144 WIRE 272 192 160 192 WIRE 512 224 512 -64 WIRE 336 272 336 240 WIRE 448 272 336 272 WIRE 336 320 336 272 WIRE -928 336 -928 256 WIRE -496 368 -560 368 WIRE -448 368 -496 368 WIRE -256 368 -320 368 WIRE -224 368 -256 368 WIRE -752 464 -752 256 WIRE -672 464 -752 464 WIRE -560 464 -560 368 WIRE -560 464 -592 464 WIRE -528 464 -560 464 WIRE -368 464 -448 464 WIRE -320 464 -320 368 WIRE -320 464 -368 464 WIRE 16 464 -320 464 WIRE 512 464 512 320 WIRE 512 464 96 464 WIRE -1568 496 -1568 -64 WIRE -752 512 -752 464 WIRE -368 512 -368 464 WIRE -816 560 -896 560 WIRE -224 560 -304 560 WIRE 512 560 512 464 WIRE 576 560 512 560 WIRE 592 560 576 560 WIRE -896 592 -896 560 WIRE -224 592 -224 560 WIRE 336 592 336 384 WIRE -1232 640 -1408 640 WIRE -1072 640 -1168 640 WIRE -1024 640 -1072 640 WIRE -960 640 -1024 640 WIRE -112 640 -160 640 WIRE -64 640 -112 640 WIRE -32 640 -64 640 WIRE 160 672 160 192 WIRE 512 688 512 560 WIRE 512 688 416 688 WIRE -1024 720 -1024 640 WIRE -112 720 -112 640 WIRE 336 736 336 656 WIRE 352 736 336 736 WIRE -1408 752 -1408 640 WIRE -752 768 -752 608 WIRE -640 768 -752 768 WIRE -368 768 -368 608 WIRE -272 768 -368 768 WIRE 512 816 512 688 WIRE -752 832 -752 768 WIRE -368 832 -368 768 WIRE 336 832 336 736 WIRE 416 864 416 784 WIRE 448 864 416 864 WIRE -640 880 -640 768 WIRE -640 880 -688 880 WIRE -432 880 -640 880 WIRE -272 880 -272 768 WIRE 272 880 -272 880 WIRE -1568 976 -1568 576 WIRE -1408 976 -1408 832 WIRE -1408 976 -1568 976 WIRE -1024 976 -1024 800 WIRE -1024 976 -1408 976 WIRE -896 976 -896 688 WIRE -896 976 -1024 976 WIRE -752 976 -752 928 WIRE -752 976 -896 976 WIRE -368 976 -368 928 WIRE -368 976 -752 976 WIRE -224 976 -224 688 WIRE -224 976 -368 976 WIRE -112 976 -112 800 WIRE -112 976 -224 976 WIRE 160 976 160 752 WIRE 160 976 -112 976 WIRE 336 976 336 928 WIRE 336 976 160 976 WIRE 512 976 512 912 WIRE 512 976 336 976 WIRE 592 976 512 976 WIRE 592 1056 592 976 FLAG 560 -64 Vs6 FLAG 576 560 Vout5 FLAG 592 1056 0 FLAG -64 640 In+3 FLAG -800 128 Byp7 FLAG -496 368 Gain8 FLAG -256 368 Gain1 FLAG -1072 640 In-2 FLAG -1472 144 0 FLAG -928 336 0 SYMBOL npn 448 224 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL pnp 272 240 M180 SYMATTR InstName Q2 SYMATTR Value 2N3906 SYMBOL diode 176 -32 M0 SYMATTR InstName D1 SYMATTR Value 1N914 SYMBOL diode 176 80 M0 SYMATTR InstName D2 SYMATTR Value 1N914 SYMBOL res 352 -16 M0 SYMATTR InstName R1 SYMATTR Value 470 SYMBOL res 144 656 R0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL diode 352 320 M0 SYMATTR InstName D3 SYMATTR Value 1N914 SYMBOL diode 352 592 M0 SYMATTR InstName D4 SYMATTR Value 1N914 SYMBOL pnp 352 784 M180 WINDOW 0 72 31 Left 2 WINDOW 3 45 61 Left 2 SYMATTR InstName Q3 SYMATTR Value 2N3906 SYMBOL npn 448 816 R0 SYMATTR InstName Q4 SYMATTR Value 2N3904 SYMBOL npn 272 832 R0 SYMATTR InstName Q5 SYMATTR Value 2N3904 SYMBOL res 112 448 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 SYMATTR Value 15k SYMBOL voltage -1568 480 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 9 SYMBOL pnp -304 608 R180 WINDOW 0 72 31 Left 2 WINDOW 3 45 61 Left 2 SYMATTR InstName Q6 SYMATTR Value 2N3906 SYMBOL pnp -160 688 R180 WINDOW 0 72 31 Left 2 WINDOW 3 45 61 Left 2 SYMATTR InstName Q7 SYMATTR Value 2N3906 SYMBOL res -128 704 R0 SYMATTR InstName R4 SYMATTR Value 50k SYMBOL pnp -816 608 M180 WINDOW 0 72 31 Left 2 WINDOW 3 45 61 Left 2 SYMATTR InstName Q8 SYMATTR Value 2N3906 SYMBOL pnp -960 688 M180 WINDOW 0 72 31 Left 2 WINDOW 3 45 61 Left 2 SYMATTR InstName Q9 SYMATTR Value 2N3906 SYMBOL res -576 448 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R5 SYMATTR Value 150 SYMBOL res -432 448 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 1.35k SYMBOL res -768 -16 R0 SYMATTR InstName R7 SYMATTR Value 15k SYMBOL res -768 160 R0 SYMATTR InstName R8 SYMATTR Value 15k SYMBOL res -1040 704 R0 SYMATTR InstName R9 SYMATTR Value 50k SYMBOL npn -432 832 R0 SYMATTR InstName Q10 SYMATTR Value 2N3904 SYMBOL npn -688 832 M0 SYMATTR InstName Q11 SYMATTR Value 2N3904 SYMBOL voltage -1408 736 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(0 100m 1000) SYMBOL cap -1168 624 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 1000n SYMBOL polcap -1488 16 R0 SYMATTR InstName C2 SYMATTR Value 47µ SYMBOL polcap -944 192 R0 SYMATTR InstName C3 SYMATTR Value 47µ TEXT -1568 1040 Left 2 !.tran 5 startup TEXT 536 968 Left 2 ;Gnd4

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bitrex 7 months ago

You'd be surprised how well a cell phone rear camera + magnifying app, secured in a set of quadhands works in a pinch..inverting the palette sometimes really helps with reading part numbers:

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john larkin 7 months ago

I use my phone as a magnifier, but the Mantis is much better for soldering or dremeling. It fills one's full visual fields, and is very

3D.

With my vision, I need magnifying eyeglasses to really see the details on my phone screen.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

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LM386 minimum count circuit

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