What is the expression for the load current of the following Operational Amplifier circuit?
Okay, so we know that the voltage at the RHS of R3 is Vout.
We know that (assuming balance) there is a virtual short between RHS of R1 &amp; R2, so the input current is Vin/4K.
So the voltage at U1+ = U1- = Vout + Vin/2, and the voltage at U1 output is Vout + Vin.
The current into RL is (Vout+Vin-Vout)/Rf , or Vin/Rf.
Output impedance is Very High (because Vout, ideally, does not depend on RL).