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[SOLVED] AC analysis in Simetrix

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hithesh123

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I just downloaded and started using simetrix last week.

I read the tutorial. But I still can't get the AC simulation right.

The amplitude vs. freq plot shows zero amplitude.
The circuit I am trying to simulate is a comparator (with reference voltage and hysteresis). seeattachment.
 

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  • LM311 comparator whyst.png
    LM311 comparator whyst.png
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When you do an AC analysis you need at least one voltage source to have 'AC 1' for its parameters, or some other value. However, you cannot measure a comparator's hysteresis with an AC analysis - you need to use a DC or Transient analysis.

Keith
 

keith1200rs said:
When you do an AC analysis you need at least one voltage source to have 'AC 1' for its parameters, or some other value. However, you cannot measure a comparator's hysteresis with an AC analysis - you need to use a DC or Transient analysis.

Keith
Click to expand...

I am not trying to measure the hysteresis with AC analysis. I just want to do an AC analysis and look at the Vout Vs freq plot.
Can you explain the AC_1 parameter?
Do you mean an AC voltage source?
I thought the waveform generator was good enough.
 

You won't get a sensible AC plot from a comparator. AC analysis is small signal - a comparator operates in large signal mode.

For an AC analysis you need a voltage source like your V3 not a waveform which is only for Transient analysis. If you edit V3 (click on it & hit F7) you will see an option to enable the AC source. If you do that (with a magnitude of 1) then you will see V3 7 0 AC 1 DC 330m appear in the netlist, or something similar.

Keith
 
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