Amplifying and filtering small AC signal with large DC offset

Discussion in 'Analog & Mixed-Signal Design' started by dmccric, Apr 2, 2019.

  1. dmccric

    Thread Starter New Member

    Apr 2, 2019
    3
    0
    I am trying to extract a small AC signal (~50mV Pk - Pk) from an Instrumentation Amplifier using a Single Supply voltage (+5V) and I want to get rid of the DC Offset (+2.5V) so I can amplify and filter the AC part (1kHz mid frequency). I want to produce a clean signal of around 700mV Pk - Pk.

    Is it possible to remove the DC Part and then filter the AC signal? I can do this with a dual rail supply but this adds further noise.

    The circuit is attached.
     
  2. ericgibbs

    Moderator

    Jan 29, 2010
    7,534
    1,520
    hi dm,
    Welcome to AAC.
    It is possible to AC couple the output from the IA amplifier.
    What are the range of frequencies required.?
    E
    EDIT:
    This similar circuit shows the method to remove the DC offset.
    AA1 02-Apr-19 12.48.gif
     
    Last edited: Apr 2, 2019
  3. dmccric

    Thread Starter New Member

    Apr 2, 2019
    3
    0
    I think I'm going to have to reduce the frequency range to 30Hz to 250Hz. Interesting circuit, applying the mid point to the positive input terminal.
    I am not getting the same output yet but I am doubling checking my circuit now.
    Thank you.
     
  4. ericgibbs

    Moderator

    Jan 29, 2010
    7,534
    1,520
    hi dm.
    When ready, post your final circuit and we can run a LTSpice simulation to check it out.
    E
     
  5. dmccric

    Thread Starter New Member

    Apr 2, 2019
    3
    0
    Thanks, I'm currently using Tina-Ti. I will have to check LTSpice out.
     
  6. Ylli

    Active Member

    Nov 13, 2015
    582
    163
    What's wrong with simply using a capacitor to AC couple the signal?
     
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