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The question is

Derive an expression for the closed loop gain of the differential amplifier.

I have solutions for these questions but the solution for this question is quite vague.

Here is the solution:

I understand part 1 and part 3, but part 2 I don't.

So looking at part 2, it starts by doing a voltage divider to find the voltage at V* by doing V1 x R4/R3xR4

The rest of the step in part 2, I don't understand.

How does it go from from V* = V1 x R4/R3xR4 then to = V1/(R1 + R3/R4)

then to = (V1 x R4/R3)/(1 + R4/R3)

Is there some steps that should be in between to show more clearly what is happening because I can't follow it. Can someone explain how to get from each step to the next?

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# Homework Help: Expression for closed loop gain of differential amplifier

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