Op-Amp Current Gain with current source

[gfd43tg]

Homework Statement

Problem #6 on the attachment

Homework Equations

The Attempt at a Solution

I am stuck because if I do KCL at the node above the current source, It seems like all of the current should go back into Rs and none from the current source goes up to Rf

 

[CWatters]

You forgot the attachment but I found it on another thread.

The current through Rf is typically written as (Vo-Vi)/Rf.

 

[rude man]

There are two sources of current into Rs, not just one!

EDIT: donpacino is right. No current into Rs.

 

[donpacino]

you want iL/is

with negative feedback, the positive and negative nodes of the op-amp should equal each other. so the negative node=0V

since the voltage at the negative node is zero, with an ideal steady state op-amp no current can flow through Rs.

so the current through rf is Is.

Use that to get you started

 

[gfd43tg]

I have it solved, thank you!

I got G = -Rf/RL