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Design >> Analog Design >> Fully Differential Amplifier and output common-mode voltage
https://designers-guide.org/forum/YaBB.pl?num=1510262735

Message started by Anna901 on Nov 9^th, 2017, 1:25pm

Title: Fully Differential Amplifier and output common-mode voltage
Post by Anna901 on Nov 9^th, 2017, 1:25pm

Hello all,

I have a problem to understand fully differential amplifiers and also their CMFB.

I learned from theory vout2-vout1=A*(vin2-vin1).

But I don't understand, how would be the output signals of a FD-Amp with supply voltages of -1.7 V and 1.7 V and an output common-mode voltage of 0.8 V regarding the input signals, as attached?

How high can be the gain?

Title: 2: Fully Differential Amplifier and output common-mode voltage
Post by Anna901 on Nov 9^th, 2017, 1:31pm

Regarding the steps of the inputs signals, I drew the output signals.
The outputs of the input signals of 50 mV and 500m V would be 26*50mV=1,3 V and 1.7 V, respectively, if the supply voltages are -1.7 V and 1.7 V with a output common mode of 0.8 V.
Is the output signals correct?

Title: Re: Fully Differential Amplifier and output common-mode voltage
Post by Frank_Heart on Nov 17^th, 2017, 10:54am

the ouput is clipped with Vin=500mV. -Frank