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Screenshot shows a simple one BJT amplifier circuit in LTSpice, 100mV 800 Hz sinewave input with the output shown in the blue trace. The green trace shows the calculated voltage gain i.e. Vout/Vin. This averages about -10 which is what I would have expected. I can't explain the reason for the glitches in the gain in 2 places: where the Vout passes through zero volts on the way up and, to a lesser extent, on the way down. (Sorry: I just noticed the names on the wires which I should have removed! Please ignore)

Dabbo
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1 Answers1

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I can't explain the reason for the glitches in the gain in 2 places: where the Vout passes through zero volts on the way up and, to a lesser extent, on the way down.

The v(Vout) / v(Vin) relationship would be a straight line if the phase angle between them was bang-on 180° or bang-on 0°. But, because they can't be (maybe a fraction of a degree difference), you will have a potential X divided by 0 scenario and that will create these artefacts.

The node names are cool.

Andy aka
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  • If you're looking for distortion, perform a FFT. You may need to turn off compression (Tools > Control Panel > Compression), set .options numdgt=7 plotwinsize=0, and perhaps decrease the step size in the .tran card. – qrk Sep 14 '22 at 16:14
  • @qrk can you explain why you have sent this comment to me? – Andy aka Sep 14 '22 at 16:15
  • Comment is for the OP, not you. Sorry about the confusion. – qrk Sep 14 '22 at 19:38