op-amp

01:26:12

english:

I want to create circuit that will perform (U3 - U1 - U2) * 2 operation using single op-amp, eg. (7V - 0.5V - 4V) * 2. I created circuit that almost does this operation but it doesn't multiply by 2. I don't know how to do that. Can anybody help and explain  required modifications ?

polski:

chcę utworzyć obwód używający pojedyńczego wzmacniacza operacyjnego, który wykona operacje (U3 - U1 - U2) * 2, np. (7V - 0.5V - 4V) * 2. Obwód nie mnoży przez 2 bo nie wiem jak to zrobić. Czy ktoś może pomóc i wyjaśnić potrzebne modyfikacje ?

published 8 years ago

tonyinselby

8 years ago

Sum all three inputs into the inverting input - remember a voltage can be negative as well as positive (so make the 500mV and 4V negative). All three resistors on the input are 250Ω with the feedback resistor 500Ω. This gives you -5V as a result, then use a second op amp as a unity gain inverter. Or swap all three inputs (so -7V, +500mV and +4V).

Daro1985

8 years ago

I made my circuit resolution experimentally. After that I did try about 20 diffrent source voltages combinations and it works so I think it's correct. I asked for circuit with a single op-amp because I've been projecting circuit in EveryCircuit in which I have to save space on plane to be able to place everything required. However thanks for answer anyway.

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