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[Cadence Virtuoso Calculator] How to calculate oscillations in the output?

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vadim888

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Dear All,

I have oscillations in my output, and I don't want to check all the time is my circuit stable (Bandgap Voltage Reference) or not.

Is there a special function which allows to measure oscillation in the node?


Best,
Vadim

- - - Updated - - -

update:

oscillation in tran analyses.
 

LvW said:
Yes. That is correct.
Click to expand...

maybe another clue from Bremen? :)

- - - Updated - - -

**broken link removed****broken link removed**

Here is my simulation result, and my voltage reference circuit.

Everything is fine in the DC domain, but in time (tran) analyses I have oscillation in the output. So the question again, is it possible to check stability in DC or something else, to be sure I don't have oscillations?
 

Your links are not working.
From what I understood is that given a circuit, you want to check whether the output is stable or not or is it exhibiting oscillation?
tstart=<<enter_time_where_you_expect_output_to_be_stable>>
tstop=<<transiet stop time>>
out=VT("<<node_name>>")
pk_to_pk_swing=ymax(clip(VT("<<node_name>>") tstart tstop))-ymin(clip(VT("<<node_name>>") tstart tstop))
you can check this pk_to_pk_swing value whether it exceeds some threshold or not.
 
If you believe the output should be settled, then something
like

max(clip(Vxxx,19u,20u)-min(clip(Vxxx,19u,20u)

would give you an oscillation amplitude number. But if
the output is still settling, or contains switching spikes
or similar artifacts, this could be bent somewhat.
 
thank you for your feedback,

I believe it will help, however, just one more question, this is my voltage reference:

Screen Shot 2016-07-28 at 17.09.01.png


is there a way to calculate is circuit stability without tran analyses? Like PhaseMargin for the OpAmp...
 

For closed loop amplifiers, I used to do what is called the three amp structure. But now, I generally break the feedback loop, insert a voltage source and do a Spectre STB analysis. I can check for the phase margin and gain margin directly. Gives me an idea whether my amplifier will be closed loop stable or not!
 

vadim888 said:
... is it possible to check stability in DC or something else, to be sure I don't have oscillations?
Click to expand...

DC operation point and current consumption will be different.
 
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