+ Post New Thread
Results 1 to 3 of 3
  1. #1
    Full Member level 2
    Points: 1,910, Level: 10
    Achievements:
    7 years registered

    Join Date
    Mar 2012
    Posts
    121
    Helped
    2 / 2
    Points
    1,910
    Level
    10

    Isolate R37 from Equation

    Hi,

    I need to Isolate R37 from the attached Equation.

    The Resistors and Vo, Vf,VCC need to be in the equation.

    Any Solution?

    Thanks,

    Doron

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 5
    Points: 53,693, Level: 56
    Achievements:
    7 years registered
    Audioguru's Avatar
    Join Date
    Jan 2008
    Location
    Toronto area of Canada
    Posts
    8,747
    Helped
    2051 / 2051
    Points
    53,693
    Level
    56

    Re: Isolate R37 from Equation

    R37 is a very important part of the circuit since it and R42 set the input voltage of the opamp, then since the opamp has a gain of 1 the output voltage of the opamp is also set to be the same as the input voltage.



    •   AltAdvertisement

        
       

  3. #3
    Full Member level 6
    Points: 2,031, Level: 10

    Join Date
    Jan 2019
    Posts
    377
    Helped
    94 / 94
    Points
    2,031
    Level
    10

    Re: Isolate R37 from Equation

    try this:
    apply voltage divider at the + input of the op amp V+ = ...

    assuming a perfect op amp, V- and output = V+

    combine R25 and R28 to one equivalent resistor

    assuming Vo is open, apply voltage divider (Vf, R21, V+ and equivalent R25-R28)

    when you have Vo = ..., replace V+ with what you got above

    follow the rules of algebra
    expand everything so there are no parenthesis and no fractions
    put all terms with R37 on one side of =, everything else on the other side
    factor out R37 and divide



--[[ ]]--