how to simulate VGA(variable gain amplifier) in cadence

[Friendcheng]

hello,everyone
i am doing a vga simulation in cadence, but i come up against difficulties:
i want to see the waveform about the gain versus the vctrl(the voltage to control the gain )to certify whether they have exponential relation
but i don't know how to do it
a reference told that i can ust pss simulation to achieve my aim
can anyone told me how to do it
or any other methods to realize it

thand you

 

[PaloAlto]

uummm, you don't really describe your circuit, but I'll try to guess what you are explaining

If you are talking about an SC circuit, then you'll need to perform a tran analysis to get the gain for a given voltage. To make the plot that you want put that voltage as a parameter and do a parametric sweep of the tran

If your circuit is continuous time, then instead of tran, you need an ac analysis. Same thing, voltage as parameter and parametric sweep

 

[abcyin]

AC analysis from the spectre is enough to detect the curve, sweep the control voltage as a variable, and after ac simulation, you will get what you want.

 

[Cesar92]

Your VGA is a continuous Variable Gain Amplifier because you have Vctrl (so, is not a VGA steep I think), so in the first you can make a AC simulation and a AC simulation with a SWEEP of Vctrl voltage variation to view the curves with differents values of Vctrl.
This method is going to be set up to see the variation of the gain and the phase according to the frequency for different values of Vctrl and like that you can have an idea on the stability of the circuit.