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Simulators >> Circuit Simulators >> How to do DC gain VS Vcm and noise analysis?
https://designers-guide.org/forum/YaBB.pl?num=1285318817

Message started by urian on Sep 24^th, 2010, 2:00am

Title: How to do DC gain VS Vcm and noise analysis?
Post by urian on Sep 24^th, 2010, 2:00am

Hi,there!
I have designed a pre-amp and what to know the ICMR and noise of it.I use spectre to do simulation.
But how to find the DC gain with common-mode level Vcm changing?
The circuit is a diff. pair with diode corrected transistors as load,and output is also diff.
I made dc sweep with variable Vcm,and plot the expression
deriv(Vout+) to see the output,is the result is DC gain with Vcm changing?

Furthemore,when I run noise analysis,I find that I can select pos.&neg output as output noise,but the input noise,but the input voltage source can only select one,and my diff.input is fed by two voltage,then what should I do?

Thanks a lot!

urian

Title: Re: How to do DC gain VS Vcm and noise analysis?
Post by sheldon on Sep 27^th, 2010, 8:19am

Urian,

In ADE, setup the measurements for the default Vcm level and then
use parametric plotting to sweep Vcm. If you setup the results to
return scalars, for example, ymax( open loop gain), the results will
be plotted vs. Vcm. Use the analogLib ideal_balun to generate your
inputs, this approach will allow you to separate differential and common-
mode inputs.

Best Regards,

Sheldon