Re: NEWBIE: Designing a Simple Audio Amp

From: John Popelish (jpopelish_at_rica.net)
Date: 01/02/05

  • Next message: Ken Smith: "Re: Bill Clinton in lewd Sex act with prostitute" 
    Date: Sat, 01 Jan 2005 20:23:48 -0500

    Anthony Fremont wrote:
    >
    > "Graham Knott" wrote:
    > > John Popelish wrote:
    > > > Forgot this one (I just bought 10 of these so I should have
    > remembered
    > > > it)
    > > > http://rocky.digikey.com/WebLib/ST%20Micro/Web%20Data/TBA820M.pdf
    >
    > > Have a look at
    > > http://homepage.ntlworld.com/g.knott/elect24.htm
    >
    > I have a question about your circuit. R2 and C3; what is their
    > function?

    At the high frequency end of the amplifiers capability, the speaker
    tends to look inductive (rising impedance with frequency), which
    raises the open loop gain, just as the phase shift of the amplifier is
    increasing and tending to decrease the stability of the closed loop.
    This network absorbs energy at this part of the spectrum, loading down
    the gain, so that the amplifier will not oscillate at a few hundred
    kilohertz, especially if you disconnect the speaker. At ordinary
    audio frequencies, it consumes very little power.

    See Zobel network on this page:
    http://www.rane.com/par-z.html 

    -- 
John Popelish
  • Next message: Ken Smith: "Re: Bill Clinton in lewd Sex act with prostitute"