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Simulators >> Circuit Simulators >> can i do nyquist criterion in cadence
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Message started by cczhang on Oct 23^rd, 2009, 1:07am

Title: can i do nyquist criterion in cadence
Post by cczhang on Oct 23^rd, 2009, 1:07am

hi i want to know can i do nyquist criterion in cadence. the version of cadence is ic5141. if it can be done, ple tell me how to do it. thanks very much

and also i want to know how to start stb simulation in cadence. thanks

zcc

Title: Re: can i do nyquist criterion in cadence
Post by buddypoor on Oct 23^rd, 2009, 1:16am

cczhang wrote on Oct 23^rd, 2009, 1:07am:

Of course, you can. All you need is an ac analysis and the capability to draw the imaginary part of the loop gain vs. the real part.

Title: Re: can i do nyquist criterion in cadence
Post by cczhang on Oct 23^rd, 2009, 1:39am

Of course, you can. All you need is an ac analysis and the capability to draw the imaginary part of the loop gain vs. the real part. [/quote]

hi ,could you explain more details how to use? thanks
for example how can i get the trans function of loop gain and how can i draw the imaginary part of the loop gain vs. the real part?

Title: Re: can i do nyquist criterion in cadence
Post by buddypoor on Oct 23^rd, 2009, 2:59am

cczhang wrote on Oct 23^rd, 2009, 1:39am:

..............................
for example how can i get the trans function of loop gain and how can i draw the imaginary part of the loop gain vs. the real part?

I am afraid you are not very familiar with the subject - and therefore, it´s not easy to explain in detail the meaning resp. simulation alternatives for loop gain. I am not working with Cadence, but with a lot of other simulation programs - nevertheless I am sure that you can ask cadence to plot IM(L(s)) if L(s) is the loop gain. And than you can change the x-axis to show R(L(s)). And this gives you the NYQUIST plot.
I repeat: At first you have to become familiar with the term loop gain - and how to simulate it. This item has been discussed very often in this forum.
Regards + good luck.

Title: Re: can i do nyquist criterion in cadence
Post by cczhang on Oct 25^th, 2009, 5:54pm

thanks very much.

Title: Re: can i do nyquist criterion in cadence
Post by larry flowers on Oct 5^th, 2012, 7:04am

Hi

If you just want results for some application purpose and this simulation is not specific to just cadence ; then i think you can do this better at MAT-LAB simmulink. Mat lab has built in function for Feedback loop gain.

For 'gain' : It is the measure of ability of a system to increase its output (Power , Amplitude) with respect to Input.
For 'Loop gain' : If this gain is controlled by some feed back then it is called loop gain.

Remember adding Loop to some system decreases its overall gain.

Nyquist Criterion : It tells whether the system under consideration is stable or not and if not stable what changes can be done to make it stable !

This is actually dealing with complex variables in terms of systems ;)
and Plotting results.

thanks

Title: Re: can i do nyquist criterion in cadence
Post by boe on Oct 5^th, 2012, 9:32am

larry flowers wrote on Oct 5^th, 2012, 7:04am:

... Mat lab has built in function for Feedback loop gain.

So does Cadence.

- B O E