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LM386 Mini Amp

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by drewlane, Mar 31, 2003.

  1. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Make the LM386 circuit that is in its datasheet.
    Its minimum supply voltage is 4V where its output power into 8 ohms at clipping is only 0.07W which is almost nothing. You are powering it with less supply voltage so if it works then its power will be less.

    It won't have interference if it is built compactly on a pcb and the input cable is shielded audio cable.
     
  2. tidos76

    tidos76 New Member

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    k thanks. are there any other amp you recommend for running on 3.6v?
     
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    3.6V is extremely low for a power amplifier and for an 8 ohm speaker.

    A TDA2822M works with a supply voltage down to 1.8V!
    It is also in an 8-pins case but is two bridged amplifiers for double the voltage swing than an LM386 and therefore its output power is about 4 times more at about 0.28W. It is still a very small amount of power so keep the volume control turned down low enough so the amplifier does not clip.
    A schematic and a pcb design are in its datasheet.
     
    Last edited: Nov 12, 2008
  4. dave

    Dave New Member

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  5. tidos76

    tidos76 New Member

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    thanks a mucho
     
    Last edited: Nov 12, 2008
  6. transistor495

    transistor495 Member Forum Supporter

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    TA7368P is an excellent audio power amp designed by Toshiba for portable applications. It has very low distortion and noise probably not at all!!
    It works well with a couple of external comps and doesn't even need an input coupling cap :p. I've made it as a rechargeable ipod power amp(6v).
    Since 1yr I'm enjoying good music thru that. The 4*AA rechargeable battery lasts without any distortion for around 2months, half hour usage perday!
    Vcc(2-10V,avg 720mW)
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

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    It has the same low output power as the LM386 power amplifier because it is a similar single-ended copy.
     
  8. transistor495

    transistor495 Member Forum Supporter

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    I've assembled LM386 only once and dropped into my toilet and flushed well with plenty of water!
    It is suitable for testing an audio sound because it amplifies.
    It is not good for a dedicated application because it produces audible noise even at low-gain configuration. No need to say about higher conf!
    TDA2822 requires higher load resistance at bridge configuration. A really mess circuit. It is mainly intended for stereo apps.
    TA7368P has a lowest possible simplified application circuit. I can't hear a little bit of noise when the volume control turned full up at no signal condition. When a signal is inputted it neatly amplifies and gives a smooth output :)
    NB: I have first seen TA7368P on the output stage of a Philips radio receiver(guess LM386 in place of that). Philips have used LA4510 on the output stage of 3v walkman superheterodyne radios(old).
     

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  9. tidos76

    tidos76 New Member

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    I think I'm going to try the ta7368pm its v rating is as low as 2v.correct me if I'm wrong. I'm not too worrid !out the size of the board as I am the thickness. So far I've managed to keep it less than 3/8" thick including caps.the thinner the better.
     
  10. audioguru

    audioguru Well-Known Member Most Helpful Member

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    No.
    Its datasheet has its bridged spec's with an 8 ohm load and a 4 ohm load for the more powerful 14-pins TDA7822 version.
    The datasheet for the little TDA7822M in the 8-pins version has its bridged spec's with a 32 ohm, 16 ohm, 8 ohm and 4 ohm load.
     
  11. transistor495

    transistor495 Member Forum Supporter

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    It will work fine at 2v. 2-10V is acceptable by the IC. Normal operation is at 6v providing an output power near to 1W.
     

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  12. tidos76

    tidos76 New Member

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    Do they make a similar chip as a surface mount? Or only through hole? Or can I simply bend the tabs and surface mount it? Lol keep in mind I'm 22 work nights and have way too much time on my hands!a Ufo is my next project!!
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

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    No.
    Its output power with a 3V supply and an 8 ohm load is only 80mW at clipping. With a 2V supply then its output power is much less, maybe only 10mW which is almost nothing.

    1W into 8 ohms is a voltage swing of 8V p-p. The swing into 8 ohms with a 6V supply is only about 4.4V p-p. The datasheet shows it clipping with an output power of only 300mW when it has a 6V supply and an 8 ohm load.

    Its output power when it has a 6V supply, a 4 ohm load and severe clipping with 20% distortion is 900mW.
     
  14. tidos76

    tidos76 New Member

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    So am I better off finding lower ohm speakers? Only reason I am using the ones I have is because they are super thin. I believe they are around 5mm. But I'm sure I can find some better. Can someone also suggest a cite about the clipping and such. I don't wanna badger you guys with noob questions
     
  15. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Speakers with a lower impedance (ohms) draw more current from an amplifier if the amplifier can supply more current. Then the power is a little more.

    An amplifier's output clips when its output voltage swing becomes the maximum that it can with a certain power supply voltage. If the volume control is turned higher then the clipping slices off the top and bottom of each wave creating square-waves and severe distortion.

    I think you are talking about using tiny speakers with an extremely low power which will result in very faint audio.
     
  16. tidos76

    tidos76 New Member

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  17. transistor495

    transistor495 Member Forum Supporter

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    No.
    I feel like a datasheet itself is talking :D
    I've got a notable performance degradation only at Vcc down to 1.8V. I've measured the voltage and I again recharged the cellpack to a maximum possible 5.5V for 4*AA cells. Current consumption is too low.
    When I'm writing this, still I'm hearing music thru it. Ahh....
    With 2v supply the TA7368P IC is capable of delivering good audible audio like any other 3V power amp IC's.
    Hi tidos,
    You can even use this IC with just 2*AA cells. Alkaline or high capacity NiMh cells will give you longer operating time. Look at the datasheet here for SMD version TA7368F, package info and other details.
     

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  18. audioguru

    audioguru Well-Known Member Most Helpful Member

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    So the "speakers" are actually earphones.
    Without an enclosure do they produce any bass frequencies?
    Why didn't you use ear-buds?
     
  19. tidos76

    tidos76 New Member

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    So am I better off finding lower ohm speakers? Only reason I am using the ones I have is because they are super thin. I believe they are around 5mm. But I'm sure I can find some better. Can someone also suggest a cite about the clipping and such. I don't wanna badger you guys with noob questions
     
  20. audioguru

    audioguru Well-Known Member Most Helpful Member

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    A 4 ohm speaker will try to draw twice as much current as an 8 ohm speaker. The amplifier will try to double the current but will provide only about 1.8 times the current.
    Then the power to a 4 ohm speaker is about 1.8 times the power to an 8 ohm speaker.
    A difference of double the power is very small because our hearing's response to loudness is logarithmic. 10 times the power sounds twice as loud.
     
  21. tidos76

    tidos76 New Member

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    sorry for the double post. thanks alot for your help. yes they are earphones. i'm integrating the unit inside my helmet so that i don't have to use earbuds. they do produse some bass. they sound similar to noise canceling headphones without the padding.
     

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