MT8870 electrec microphone in

Discussion in 'General Electronics Chat' started by Razor Concepts, Nov 1, 2009.

  1. Razor Concepts

    Thread Starter Active Member

    Oct 7, 2008
    The MT8870 is a common DTMF decoder, it uses an audio-in signal. Here is the common schematic:
    Some of the values vary a bit depending on the schematic but the basics are the same.

    However, I want to use an electret microphone as the input audio source. What kind of amplifier circuit do I need to put in between the electret microphone and that circuit above? Thanks!
  2. beenthere

    Retired Moderator

    Apr 20, 2004