how to simulate "gm" of an OTA?

[cqmyg5]

how to simulate gm

Hi,

As "gm=Io/Vin", AC simulation could get Vout/Vin, but how to get the small signal Io?

I searched here, some thread said to build a RC(1Gohm and 1F) negative feedback to cancel offset, I don't understand that purpose.

 

[pfd001]

hspice gm ota

OTA is used in open loop. According to definition of gm, you should add a large capacitor at the output to make it ac ground. Then do ac simulation, you will get small signal Io

 

[cqmyg5]

ota gm spice

Thanks!

How to print out the Io with hspice? what command I should use?

 

[zizu]

how to simulate ota

Check .print .plot .probe commands in Hspice manual, ex. .probe i(CL), CL is the element name of the large load capacitor.