- #1
leroyjenkens
- 616
- 49
Homework Statement
I need to derive this expression [itex]v_{out}=\frac{1}{2}(v_{1}-v_{2})(\frac{R_{3}+R_{2}}{R_{3}})[/itex]
Using the circuit I'm given. I uploaded it.
The Attempt at a Solution
So far I have [itex]v_{in}=v_{+}+v_{-}[/itex] which is from "rule #2 of op amps", which is "The feedback in the op-amp circuit drives the voltage differences between the inverting and non-inverting inputs to zero."
And since the circuit looks like a voltage divider, I can use the voltage divider equation to get [itex]v_{out}=v_{in}(\frac{R_{2}}{R_{1}+R_{2}})[/itex], which gives me [itex]v_{out}=(v_{1}+v_{2})(\frac{R_{2}}{R_{1}+R_{2}})[/itex], but I can't figure out why there's a [itex]\frac{1}{2}[/itex] in front of the equation that I'm given at the beginning, or why the term with the resistors is the inverse of mine.
Thanks.