chris91'
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Hello, i'm a new member and i would like to ask something that is bothering me for many days.
(of course you can remove my post to a more suitable topic but i couldn't find anything similar).
I have to design a fully differential op amp with an ICMR of 0.8 to 2.2V. I've chosen a two stage architecture (the second stage is a common source and the first one is a cascode differential stage).
I've also added a current buffer (common gate) for the zero. My question is about the measurement
of icmr. The main problem is the following. When I change the common mode input voltage of the op amp in order to check the icmr, the input of the second stage is moving and as a result of that the second stage is not working properly. So my op amp works for 1.5V dc input, but when i change it to 1.2 or 1.8V nothing works. Should I add two cmfb circuits? (i'm using ami0.6 technology) thank you
(of course you can remove my post to a more suitable topic but i couldn't find anything similar).
I have to design a fully differential op amp with an ICMR of 0.8 to 2.2V. I've chosen a two stage architecture (the second stage is a common source and the first one is a cascode differential stage).
I've also added a current buffer (common gate) for the zero. My question is about the measurement
of icmr. The main problem is the following. When I change the common mode input voltage of the op amp in order to check the icmr, the input of the second stage is moving and as a result of that the second stage is not working properly. So my op amp works for 1.5V dc input, but when i change it to 1.2 or 1.8V nothing works. Should I add two cmfb circuits? (i'm using ami0.6 technology) thank you