The picture is my circuit:
I want to find a suitable R4 to make Vout/Vin = -120
This operational amplifier is an ideal operational amplifier. Considering that there is a virtual ground at the inverting input terminal, the equivalent resistance above is (R2||R3)+R4, and then use the inverting amplifier to calculate the gain formula G=-[(R2||R3)+R4]/R1, I calculated that R4=120MΩ, but I see that the simulation of others is 24kΩ. What is wrong with my thinking?
Kenzie ポストする September 14, 2020
Are you sure that R1 is 1MΩ?
Lexi ポストする September 14, 2020
Yes, you can look at the simulations of others I saw
Kasey ポストする September 14, 2020
As a reminder, the input current of an ideal op amp is zero.
