about OP177 amp how work

how the circuit worhs,how the relationship between output and input is calculated and derived.

  • +1
    •  Analog Employees 
    •  Super User 
    on Feb 6, 2020 1:51 PM

    Vout = Vin × (R5+R4R)/R4;

    This is a composite amplifier , and U2 is first stage as a error amplifier, U1 is second stage for output. 

    The circuits is not stable in practice, it may oscilate.

    As usual I will design a integrator for the first stage, the RC of the integrator will solve the stability of the circuits. Like this: