Audio power amplifier IC to operate on ~3 V ?

Discussion in 'General Electronics Chat' started by Externet, Jan 23, 2016.

  1. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
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    Need to get the maximum power possible from an audio amplifier IC powered by a Li-ion cell. The common LM386 is listed as 4V supply minimum.
    Ideally , 1 watt+ monophonic into a common 4 to 16 Ω speaker, voice range.
    Thinking on canibalizing the amplifier chip from a defunct cell phone, unsure if there is better others.
    Any suggestions ?

    Something I have never done or heard... What would happen paralleling two identical amplifiers, inputs and outputs ?
    Like this ----> http://www.aliexpress.com/item/5PCS...52&btsid=397f53fd-5080-4171-b9b4-ecf66b1b24a2
     
    Last edited: Jan 23, 2016
  2. kyka

    New Member

    Jun 7, 2015
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    Just use a different audio opamp with external current booster. A good one is the ne5532.
     
  3. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
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  4. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    Use mouser search for some ideas..
     
  5. #12

    Expert

    Nov 30, 2010
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  6. kyka

    New Member

    Jun 7, 2015
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    No. Since you want 1 watt for a 4 to 16 ohm load, then your amplifier must be able to supply 0.5A RMS or 0.707A pp and ne5532 can't do that. That's why you need an external power transistor to handle the extra current.

    Then thing is, that for a 16 ohm load at 1 watt its voltage must be 5.6V pp which exceeds your voltage supply. So, you must either use a power supply booster (like the one you posted) or use an inductor to transform its impedance.
     
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    A 5532 will not operate usefully on 3.6 V, and most rail-to-rail opamps can not make enough output current to push 1 W into 4 ohms.

    For 1 W into 4 ohms you need 2 V RMS, which is 5.7 V peak-to-peak. Obviously greater than 3.6 V, so all traditional methods are out. With a configuration called Bridge-Tied Load (BTL), two output amplifiers are driven 180 degrees out of phase, and the speaker is connected directly to both outputs. Neither speaker connection goes to GND. This effectively doubles the effective power supply voltage to the circuit. With two output stages, each with a total headroom requirement of less than 1.5 V, this can be done.

    BUT, those stages need to be able to supply 0.5 Arms or 0.71 Apeak, not the typical 20 mA of an opamp. Look at TI and Maxim for Class-D power amplifiers. Someone out there makes a part with two class-D outputs designed for BTL, but I don't remember who cause I don't use these parts.

    ak
     
  8. dannyf

    Well-Known Member

    Sep 13, 2015
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    The standard power IC for low voltage application has been tda2822. the up-and-coming one is tda1308.

    TDA1308 is now my go-to IC for a lot of opamp applications outside of AF.
     
  9. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
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    Thanks, fellows.
    Even if there is a bridge-tied IC rated at 7W output and useable on 3V supply, does not mean it is applicable, as the rated output is not reached at such low supply; like the monophonic-bridged TDA7266 :

    Power vs. supply.png

    So I need to respect the suggestion of raising the supply voltage. Maaany years ago, Bose made car compact amplifiers using 1Ω speakers to get away with the 12V supply and yield higher power than their competitors. Will check for very low impedance speakers too.
     
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