- #1
cyeokpeng
- 69
- 0
Hi,
Just a little question.
The question wants me to obtain an expression for v0 as a function of v1, v2 and vcm, and show how the commom mode signal vcm can be canceled from the output by a proper adjustment of one of the resistors, R3, R4 or R5.
To find v0, I have to apply the theory of superposition.
Output voltage due to v2 alone (v1=0, vcm=0) is
--> The voltage at the output of the lower op amp is (-R4/R3)v2
--> The voltage at the output of the upper op amp is -(R2/R5)*voltage at
the output of the lower op amp.
My question is: Why is R1 not considered in the closed loop voltage gain of
the upper op amp?
Thanks
Just a little question.
The question wants me to obtain an expression for v0 as a function of v1, v2 and vcm, and show how the commom mode signal vcm can be canceled from the output by a proper adjustment of one of the resistors, R3, R4 or R5.
To find v0, I have to apply the theory of superposition.
Output voltage due to v2 alone (v1=0, vcm=0) is
--> The voltage at the output of the lower op amp is (-R4/R3)v2
--> The voltage at the output of the upper op amp is -(R2/R5)*voltage at
the output of the lower op amp.
My question is: Why is R1 not considered in the closed loop voltage gain of
the upper op amp?
Thanks