Test bench of OTA parameter measurement in CADENCE

[rajeshree]

Hello every one,

I have attached design of programmable OTA. but i dont know how to measure parameters like gain, phase, CMRR, PSRR, slew rate etc. To measure all this parameters i have used one test bench which is also attached here.
But problem is that i have measured gain in db, which is negative and phase is also negative.
In test bench there are 3 output terminals two of them are outp and outn but third one is cmref. where can i connect in my design? and what are the suitable values for all R and C in test bench. is it correct test bench?
How can i get positive phase and gain(dB)? i have attached these graphs also.
please give me suggesion
Thanks in advance

 

[richaphy]

To measure CMRR you have to connect both the input to a common input and measure the output, ie plot the output ac_magnitude, and see the value of gain, the difference between differential and common mode gain will give u CMRR. For PSRR make AC_input zero and give AC to the supply (VDD) and measure the gain from ac_magnitude plot, same way u did for CMRR.