Discussion in 'Homework Help' started by Voltage87, May 11, 2009.

  1. Voltage87

    Thread Starter New Member

    May 11, 2009

    i ve got a homework and that is to design a audiopreamplifier with op-amp(s).
    Input signal : U_e = 1 V, Sinus, 1Khz
    Output signal: variable Amplitude with same frequency and variable amplification factor between 0-5. I ve create a circuit but i am not really sure how to deminsion it.

    P.S. the graphic includes german resistance cause i am from Germany :)
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    One generally uses a fixed gain amplifier stage, and feeds the signal in from the wiper of a pot to get the 0 - 100% variance. A follower with gain would be best, instead og the inverting amp you have drawn.
  3. PRS

    Well-Known Member

    Aug 24, 2008
    Hi Voltage. Beenthere's advice is the way I'd do it. But wait a minute. You are showing an inverting amp where the voltage out is out of phase with the input voltage. I don't know the original problem, but if you want a gain of +5 volts you need to use a noninverting op amp whose gaine is Rf/Rs + 1.