Stability Analysis of Multiple Opamp circuits using LTSPICE

Thread Starter

hoyyoth

Joined Mar 21, 2020
170
Dear Team,

I need to find the phase margin of the below circuit. It contains 3 opamps.I found a method in ADI website (https://www.analog.com/en/education/education-library/videos/5579254320001.html)

They are breaking the loop and applying the stimulus. In my circuit, 3 loops are there do I need to break each loop and apply stimulus individually
and test the circuit.
My LTspice file is attached here.In this one component is from TI (LMC662A/NS).

My schematic given below for your reference
1635328167255.png

Regards
HARI
 

Attachments

ericgibbs

Joined Jan 29, 2010
14,147
Hi HARI,
Do you have the model or .net file for the LMC662A, that you could post.?
E

Update:
What is the purpose of this circuit.?:)
 
Last edited:

Thread Starter

hoyyoth

Joined Mar 21, 2020
170
Hi Eric,

Thank you very much.
May I know will we get phase margin from .AC analysis.

This circuit is used to measure voltage from a source which has an O/P impedance in the range of Tera ohms.
The output voltage is 36V to 38V that is why I bootstrapped the rails

Regards
HARI
 

Thread Starter

hoyyoth

Joined Mar 21, 2020
170
Hi Eric,

Supply voltage is -10V only .I forgot to update the net name.
May I know how to find phase margin.

Regards
HARI
 
Last edited:

ericgibbs

Joined Jan 29, 2010
14,147
Hi HARI,
I know the data sheet states 1Tohm, but the LTS model shows 100k, so be aware if you add any circuit on a LTS sim to the OPA input, it may give misleading plots.??

What will be the input source and signal levels.?

Where did you get the model.?
E
 
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