Help measuring gain...

Discussion in 'The Projects Forum' started by circuitnub, Apr 27, 2009.

  1. circuitnub

    Thread Starter New Member

    Apr 27, 2009
    I have a cascade of two BJT transistors, and I'm trying to make the gain be within a certain range. I am using PSPICE and I'm not sure how to tell what the gain is at a certain frequency. How do I check?
  2. StayatHomeElectronics

    Distinguished Member

    Sep 25, 2008
    The voltage gain is simply the output voltage over the input voltage.

    A = Vout/Vin

    There are several ways you can do it in PSPICE. You can input a given frequency and watch the response of the circuit over a given period of time. Compare the magnitude of the output signal to the input signal.

    A second way to do it is to perform an AC Sweep. It allows you to select a beginning frequency, an end frequency, and number of points you would like to simulate. A graph of the output can be plotted to show the gain.

    Here is a website that shows have to do it in one version of SPICE. Yours may or may not be similar but it might help a little. Sweep (Frequency) Simulation in PSpice.pdf
    Last edited: Apr 27, 2009

    AAC Fanatic!

    Jul 1, 2008
    Most Spice programs provide both DC Transfer Characteristic and AC Transfer Characteristic used for this purpose.
  4. circuitnub

    Thread Starter New Member

    Apr 27, 2009
    Thank you so much. Helped a ton.