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

Signal with AC and DC how to amplify only AC?

  1. Mar 3, 2008 #1
    Hi, I have a sine-wave that has an AC component (that's very small -- mV range) and a DC offset (few volts). Can someone point me in the right direction as far as amplifying only the AC component?

    Also, does anyone know an alternative to PSpice Student... I get max'd out at 64 nodes, so I can't any simulation if I exceed that value. Thanks.
  2. jcsd
  3. Mar 3, 2008 #2
    filter out the dc component. Take the AC/DC go through a high pass filter (either RC,LC,op-amp depending on cutoff). These will remove the Dc offset.
    Then a rail-rail op-amp to amplify the AC signal. Use a low noise amplifier like a JFET.
  4. Mar 3, 2008 #3


    User Avatar

    Staff: Mentor

    Yeah, just AC couple the signal into your opamp circuit through a capacitor. Choose the capacitor value to put the HPF pole (the C in combination with the equivalent input R of the opamp circuit) a couple octaves below the AC component's frequency.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook