For the op amp below
- Open-loop gain is \$A=2\times10^5\$
- Input resistance is \$R_i=2\,M\Omega\$
- Output resistance is \$R_o=50\,\Omega\$
I am asked to calculate the close-loop gain \$Vo/Vs\$ and find \$i_o\$ when \$V_S=1\$ .
(Schematic diagram above from "Fundamentals of Electric Circuits" by Charles Alexander and Matthew Sadiku.)
Then I've redrawn the circuit and defined the currents as shown in the figure.
Then according to those currents above I've applied KCL and also I've got these equations below.
\$I = I_1+I_2\qquad I_2=I_3+I_4\$
$$A \times V_d=2\times10^5\times 2\,M\Omega\times I$$
Then I've also written some equalities according to KVL in the closed loops but I was never able to find a relation between \$V_S\$ and \$V_o\$ or just ended up crosschecking the same equations. It all got tangled up.
- How would you solve this?