How to amplify ac square wave

Discussion in 'General Electronics Chat' started by mbird, Feb 2, 2009.

  1. mbird

    Thread Starter Member

    Jan 29, 2009
    24
    2
    Hi --

    I have a CMOS chip and I generate a square wave with changing frequency. It is LVTTL (3.3Volt) and max current from the device is 24mA.

    I want to drive a speaker in both directions with it so I added a capacitor such that RC>>Frequency of my square wave (I think this method is called coupling capacitor?). That worked and produces a nice AC square wave -3 to 3 volts.

    Now I want to amplify this AC square wave so I can get up to 250mW for my speaker.

    I can see how to amplify current for a DC square wave with a single transistor but how do you amplify an AC square wave? Can it be done with simple transistor amplifier? Do I need an Op Amp (but looking at those it seemed like they are not the right choice for driving a speaker?)

    I did a lot of searching on the Internet for how to do this but nothing seemed right so I am posting here.

    Thank you!
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    I answered your questions on another website.
     
  3. secrect

    Member

    Feb 1, 2009
    16
    0
    could you give the link of your another website?
     
  4. mbird

    Thread Starter Member

    Jan 29, 2009
    24
    2
  5. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    I know how you feel. :)

    I once have a case where the OP ask the same question again on another website but with comments like "Some guys told me to use/do xxxx, what do you guys thinks".

    I nearly replied "That's rubbish, don't listen to a single word he said." :D

    Sorry to OP for hijacking the thread.
     
  6. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Use an op amp to amplify the voltage and then use a transistor in an emitter follower configuration to drive the speaker. The best solution, however, will be an audio amplifier. Have a look at www.national.com for audio amplifiers integrated in a chip.
     
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