Differential amplfier - CMR adjustments

Discussion in 'Homework Help' started by biologyfreak2008, Nov 26, 2008.

  1. biologyfreak2008

    Thread Starter New Member

    Nov 26, 2008

    I've got a question concerning an ECG measurement I did at a laboratory lesson recently. The amplifier was a 3-OP circuit with two adjustable potentiometers. We were to adjust those to get a minimal common mode signal at two different frequencies (100 Hz and 1kHz). What I can't understand is why you have to do this att two frequencies?
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    If you are in a country that uses 50 Hz power, the the 100 Hz test was to eliminate power supply interference. It should be valid for 120 Hz as well. The 1K test was to insure any interfering frequencies outside the range of interest was eliminated.