ICMR of a differential Amplifier

[suhas_shiv]

Hi all,

How do I find (by simulation in Spectre) the Input commom mode range of a Diff Amp? Meaning, how should I give the inputs? The frequency of operation is 600MHz and input differential signal voltage is 100mV.

Thanks in advance.

 

[vbhupendra]

if I1 I2 are the inputs
then
put
V1 I1 I VID
V2 I I2 0
V3 I 0 VINCM
then sweep V3 from 0 to VDD
plot tail current vss V3 will give Vincm(min)
plot ID(load) will give Vincm(max)

 

[dasong]

You can simulation in close loop.make DC simulation,watch the output voltage,and the range of PSRR decrease 6dB is CMIR