Operational Amplifier Homework Question

[Ariastity]

Homework Statement

What is the value of V2 in terms of Vos?

Homework Equations

The Attempt at a Solution

In the class, we were told that this is just a non-inverting amplifier, thus V2= Vos x (R2/R1+R2).
However, I want to work out the solution by applying nullator hypothesis (voltage difference between the two op amp inputs is 0) only, without realising that the top part is a potential divider.

Is it correct to assume that the voltage across R1 is Vos? That way, I can get the current i to solve for the voltage across R2.
http://[PLAIN]http://i64.tinypic.com/a0i5hs.jpg
http://i64.tinypic.com/a0i5hs.jpg

 

[gneill]

Is it correct to assume that the voltage across R1 is Vos? That way, I can get the current i to solve for the voltage across R2.

Yes, that's a valid assumption here.

 

[rude man]

In the class, we were told that this is just a non-inverting amplifier, thus V2= Vos x (R2/R1+R2).

A non-inverting op amp gain is always >=1 unless the feedback is active (another amplifier section). So I hope you were not told that ...
... and I assume you meant Vos x R2/(R1+R2) otherwise your equation is dimensionally wrong.

 

[LvW]

Is it correct to assume that the voltage across R1 is Vos? That way, I can get the current i to solve for the voltage across R2.
http://[PLAIN]http://i64.tinypic.com/a0i5hs.jpg
View attachment 110118

Yes - with this assumption you get I=Vos/R1=(V2-Vos)/R2.
This equation can simply be solved for V2.