how to simulate fully differential opamp

[avinash]

how the gain,ugb and phase margin can be calculated of fully differential opamp.pl help

 

[glenjoy]

Gain is always computed by the external resistors, that is the property of the OP-AMP.

 

[opamp741]

r u talking abt hand calculation or using simulaton tools..

 

[avinash]

dear opamp741,
i am asking to calculate gain ugb and phase margin through simulation tool.

 

[ezt]

Hi.
I think you can simply use probes (e.g. voltage probe) to check the gain of your circuit. but before that you should set up your analysis (frequency Analysis in your case). then you will run it and you can check the results in probe window. (this is the way in almost every simulation tools, but ofcourse with some changes in names)

Regards,
EZT

 

[v_naren]

how the gain,ugb and phase margin can be calculated of fully differential opamp.pl help

Here is the solution to your question!

https://www.designers-guide.org/Analysis/diff.pdf

and




if I have helped you could you please kindly click the "helped me" button and help me....you dont loose any points at all

Good Day!

Best of luck!

 

[chinito]

better yet, cadence has a white paper called characterization of diff amp. It will teach you how to use spectre to find whole bunch of things.

 

[avinash]

if i want to characterize the fully diff opamp in hspice,what should i do.

 

[v_naren]

if i want to characterize the fully diff opamp in hspice,what should i do.

which is why I recommended

https://www.designers-guide.org/Analysis/diff.pdf

and

 

[avinash]

dear v_naren
the pdf link given by you does not provide me the information about getting the ugb and phase margin.pl tell me some method.
moreover to calculate gain in single ended opamp,we provide ac signal to +input and connect the -ve input to output with RC .
but what should i do in case of diff o/p.

 

[lilac]

hi avinash,
I usually provide two oppsite ac signals to input+ and input-. and of course, connect two output with load capacitors. Then do ac analysis, and check the result of AC magntude & Phase for the ugb and phase margin.

 

[avinash]

dear lilac,
on which o/p node should i check for the gain,ugb and phase margin.moreover you havenot provided any feedback.

 

[naisare]

When Ac analysis is given, first it find out the dc node voltages upon which it does the frequency analysis. So, it is important that the dc voltages are established earlier. This will be a problem if u r using a switched capacitor CMFB for the diff amplifier. first u need to run the transient with the clocks of the CMFB till the opamp output reaches the stable dc voltage. U can load this node voltages as the initial node voltages and do the ac analysis on this.

 

[lilac]

hi avinash,
yes, what I said above is the method to measure the AC open loop spec. of opamp.
Please refer to this document, I think you can get what you want to know!

 

[avinash]

dear lilac, which document are you talking about.

 

[lilac]

Hi vavinash,
I don't know why I cannot attach it on.
So, try one more time!
If you still cannot see it, leave your email address, maybe I can email it to you!