1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Transfer functions in op amps

  1. Mar 12, 2008 #1
    I have a question regarding finding the transfer functions when dealing with op amps. I do not understand the steps towards going from a general op amp circuit towards getting an the transfer function where you can draw the bode plots for magnitude and phase. Could anyone give me a general step by step tutorial for finding this function or give me a website where they go in depth with these types of problems.
  2. jcsd
  3. Mar 12, 2008 #2


    User Avatar

    first you need to confirm that the op-amp is configured to have negative feedback (that they didn't wire it up backwards), so it's a linear circuit.

    then, define the current going into the "+" and "-" terminals is zero (because of the extremely high input impedance) and define that the voltage difference between the "+" and "-" terminals is zero (because of the extremely high gain of the op-amp).

    then you apply either the Loop-Current method or Node-Voltage method of circuit analysis, along with the known volt-amp characteristics of every other component in the circuit. this can also be done with the frequency-domain volt-amp characteristics, which is what you want to do if you are seeking frequency-domain behavior (which is what the transfer function is) instead of time-domain behavior (which is what the impulse response or step response are).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook