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Question about total GM in single-end and differential op-amps

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Dear all :
I have some question about total GM in
single-end and Differential OPAMP.

The single-end and Differential GM are all gm1, am I right ?

Thanks .
 

about total GM

That's right
 

about total GM

yes you are right,
GM of the opamp normally refers to input stage.
 

about total GM

yes,you can get the GM if the voltage gain is devided by the output resistance.
 

about total GM

TOTAL GM WILL BE CHANGE IN OUTPUT CURRENT/CHANGE IN I/P VOLTAGE
 

about total GM

The first one is correct, however,
for the second one, the total GM is
just HALF of gm1,2.
 

about total GM

Pls check sec 4.2.2 in Razavi for more detail.
The 2nd ckt has GM=gm1 only if the differential input signal is small.
 

about total GM

Dear gte582w :
why for the second one GM=1/2gm1 ?
total gain = Gm*Rout
=gm1*Rout
I sim AC/Trans are all show me the
total gain = Gm*Rout
=gm1*Rout
= 20log(vop-von)/(vip-vin)
Could you explain it for me ?

thanks.
 

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