how to simulate common mode input range of telescopic OTA

[umount]

how to simulate common mode voltage

i searched a lot. And many people said "configure your op-amp as unity gain buffer. Now, sweep your DC input, and plot output vs input.The linear region in your output with gradient 1 is your ICMR."

I think this is right. but as we know, telescopic OTA has a smaller ICMR, and is not easy to connect its output to its input directly. So in this case, how to simulate its ICMR?

Pls help me out. Thank you!

 

[DenisMark]

Use ideal OPAMP with unit gain, pos input connect to output of ur OTA, neg input to dc source with desired output voltage. Output of OPAMP will be offset voltage, futher u need to apply this offset voltage to inputs of OTA through voltage controlled voltage sources to eliminate offset of OTA.
ICMR i define as -3dB lost in gain when i do AC sweep analisys over CM input voltage. See "Characterizing Diff. Op-amps - Cadence from jonathan David" on

 

[pankaj jha]

can anyone provide me a OTA circuit schematic. i wanna simulate it in candence....