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A question on result non-consistent between OP and Transient

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There is a small circuit I simulated and found inconsistent. In the spectre.out, the value on a
 transistor is :  gate 1.95651 V, drain 5.59709 uV, source 4.00421 uV, Ids = 159.733 pA.

However, the direct plots of transient results shown in waveform are totally different, as shown
 in the figure.  So what will cause the inconsistence, and which one are the correct results ?

I think this is actually a common question as I encounted similar things before, which touches
fundamentally how the simulation works.

Best regards,

Sz5g


Originally posted in cdnusers.org by sz5g

  • The question cannot possibly be answered, since you've not explained how the values in the spectre.out were simulated (was it from a DC simulation, an info analysis or what?). You've not explained what the transient was doing - are the conditions the same as DC? I notice there's a step at the start of your simulation results above. Also, the net names above and current measurement give no indication of which signal is which.

    Remember that people don't have extrasensory perception in general - and it's hard to debug something without complete information.

    This is most likely to be a setup mistake or a mistake in interpreting what you've done - but without seeing the full picture I can't pinpoint what is wrong.

    Regards,

    Andrew.


    Originally posted in cdnusers.org by adbeckett

  • Andrew:

    Thank you very much for your questions, which lead to the solution finally. An initial condition causes
    the difference.

    A related question will be: after " oppoint" calculated by using initial condition, will later on the "oppoint"
    values be changed based on changing node values ? so that all calculations based on "oppoint" will be
    updated accordingly ? Guess it should be.

    sz5g


    Originally posted in cdnusers.org by sz5g

  • Sorry, I don't understand your question...

    Regards,

    Andrew.


    Originally posted in cdnusers.org by adbeckett

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