Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Modeling the Input Impedance of an Amplifier

  1. May 25, 2006 #1
    I'm trying to model a circuit. Part of this circuit is a guitar amplifier. I don't know what kind of circuitry is inside the guitar amp, it manufactures often list the input impedance in the product specifications.

    When they say input impedance, do they mean the impedance between the signal input and the ground? Can I simply treat the input impedance as a resistor?
     
  2. jcsd
  3. May 25, 2006 #2

    berkeman

    User Avatar

    Staff: Mentor

    Yes. The input circuit for an input like that will generally look like a resistor for small signals.
     
  4. May 25, 2006 #3
    Would it be correct to say that for AC signals there is negligible capacitance and negligible inductance?
     
  5. May 25, 2006 #4

    berkeman

    User Avatar

    Staff: Mentor

    For the audio amp you mention and for audio signals, then yes, the input impedance should not present much series inductance or parallel capacitance. Otherwise, it would distort the audio signals. Well, I guess that can be a desired thing sometimes with an electric guitar....:devil: :biggrin:
     
  6. May 26, 2006 #5
    Generaly there shouldn't be signal distortion, but if there is a 1dB roll off around 4KHz I'd like to know about it.
     
  7. May 26, 2006 #6

    berkeman

    User Avatar

    Staff: Mentor

    Well, you'll only be able to determine that by testing, or by getting the actual schematic for your simulation. You can't use "black box" specs for a detailed simulation.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Modeling the Input Impedance of an Amplifier
  1. Input Impedances (Replies: 3)

  2. Input Impedance MESFET (Replies: 3)

  3. OP AMP input impedance (Replies: 2)

  4. Input impedance (Replies: 12)

Loading...