Hello,

I have the problem that the maximum supply voltage I can use is too small for the design of a gilbert cell. I decided to bias the transconductance stage of the gilbert mixer without a current mirror at the button. So I need to bias the BJT transistors like current mirros itself. Can somebody explain, what is the drawback of this ? I heard that when doing so you won't have AC common mode voltage rejection. Is that right and why ? Thanks for response.