why does opamp cmrr degrades with frequency

[zoulzubazz]

hey folks,

I have been using opamps for few years now, but I have been wondering the past few days why the CMRR of an opamp degrades with increasing CMV frequency. does this have to do with the input stage of the opamp. Thanks.

 

[FvM]

does this have to do with the input stage of the opamp.

Not necessarily. Common mode rejection is also related to supply voltage rejection. If you assume the supply crosstalk located in the second or output stage, the open loop gain frequency characteristic would already explain the CMRR drop. In practice, expect a combination of all factors. Perform an exact circuit analysis if you are interested to know more.