Question about Cadence Sim: Gm and Rout

[haoyun]

Hi everyone,
How to get "Gm" and "Rout" curve of a OTA using cadence? DC or AC?

Thanks

 

[abcyin]

Hi,
as to the Gm simulation, you can use "DC" analysis to sweep input differential voltage, and detect the output current, and then use "deriv" function in the calculator.
for Rout, use "SP" analysis, you can get parameters such as Z11, Z22, etc. and Z22 is what you want.

Hope it helps!

Added after 5 minutes:

Of course, you can still use "AC" analysis to get the output impedance, just pour in an AC current signal, one ample for example, detect the AC voltage on the output net, that's the value for Rout.

 

[obi1]

Remember that Gm must be calculated with Vout=0 and Rout for Vin=0

 

[dipanjan]

hi...can u tell me more about sp analyisis in cadence analog design tool.what arte the parameters you use for the analysis to obtain Rout
also as noted how do u get gm for vout =0?????
i am designing an opamp and as for mos opamps we gen use capacitive load instead of resistance can neone plz tell me when we giv a diff input to a diff amp with a capacitive load....what is the output patern i am expecting.
it would be very helpfull if i can get a graph but even a explanation will do
thank you all in advance. really need your help.