connect LM324 to an 8 ohm speaker

Discussion in 'The Projects Forum' started by alexpanrui, Apr 3, 2008.

  1. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    dear all,
    anyone could help me with the connection between a LM324 and an 8 ohm speaker...thx a biiiiiiiiiiiiiiiillion
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    I don't think an LM324 has the schtutz to drive a speaker directly but it would start with a blocking capacitor to the speaker to ground.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Consider using an audio amplifier, like an LM386.
    http://www.national.com/mpf/LM/LM386.html

    There are many other audio amplifiers, but LM386 are very common, easy to get, and cheap.

    Download the datasheet (available at the above link) and have a look at the Typical Applications section on page 5.
     
  4. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    thank both of u for the quick reply...but the chip lm324 is provided by my lecturer...so i guess i have to use it...papabravo, i dont get u...i'm pretty new to circuit design...thx
     
  5. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    See page 9 (power amp) of attached datasheet:
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    What's not to get? How much current can an LM324 source or sink. Is enough to move the voice coil?
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Can you add external components? Things like transistors?
     
  8. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    yes,adding external components is allowed
     
  9. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    papabravo,thx for ur advice....i will figure it out
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    Bravo! -- Good luck to you in that effort. Check back if you get stuck.
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    An LM324 can output a peak current of 20mA. The RMS current is 14.1mA and the RMS power into an 8 ohm speaker is only 1.6mW. Earphones are much louder.

    The LM324 "power amplifier" applies a bias voltage of 6V to the speaker that might push the cone so far out of the magnetic gap that the speaker will perform like a rectifier.
    The DC current is high enough to melt a little speaker.
     
  12. Papabravo

    Expert

    Feb 24, 2006
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    You know these things, and I know these things, and many other forum members know these things. I was kinda hoping the OP would discover these things on his own. He seemd to have just a modicum of industry.
     
  13. Audioguru

    New Member

    Dec 20, 2007
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    You want him to learn the hard way?
    I learned about circuits before I blew anything up.
     
  14. beenthere

    Retired Moderator

    Apr 20, 2004
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    Yes, but the stuff you learned after the smoke cleared meant a bit more.
     
  15. alexpanrui

    Thread Starter Active Member

    Feb 25, 2008
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    yo,thank u all...finally i heard something from the speaker...and one more thing i wanna clarify is that MY LAB OFFICER FORGOT TO GIVE ME LM386!!!!!!!!!!!!!!!!!!!!!!!!I bought one and am testing it now...basically the analog output is from DAC0832...I connect this output to LM324 which is working as a voltage follower (buffer)..and i fed the output from LM324 to LM386 which drives an 8 ohms speaker....i can hear something from the speaker,but the sound doesnt sound ok.....its like siren alarm...ive wrote a small piece of program which feeds in 0x00 and 0xff to DAC continuously...shouldnt the sound be consistent?wat could be the problem???
     
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