# Ideal Op-Amp question

1. Sep 17, 2012

### spoonjabba

Derive a symbolic expression (i.e., a formula containing symbols R1, R2, ..., etc., andarithmetic operators instead of numerical values) for the voltage gain of the amplifier

What im stuck at is the two nodes on each side of R4

I initially disregarded the node to the right of R4, which was wrong. since there is a virtual sc at the input of the op amp terminals what would i consider the node on the right of r4?

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Last edited: Sep 17, 2012
2. Sep 17, 2012

### lewando

Since no current is flowinginto either -/+ terminal as well, the voltage at the + terminal is 0V.

3. Sep 17, 2012

### rude man

You just said to consider the node on the right of R4 to be a sc which I assume must mean short circuit or, as we call it, ground. The problem?

4. Sep 17, 2012

### uart

You could also replace Vi, R3 and R1 with their Thevenin's equivalent and then just analyze it as a standard inverting amplifier.