Amplify cellphone audio output

Discussion in 'General Electronics Chat' started by scriptr, Sep 17, 2010.

  1. scriptr

    Thread Starter New Member

    Sep 17, 2010
    2
    0
    Hi,

    I am working on a project which is controlling a device that plugged into cellphone's audio jack.

    My device needs at least 2.5V to work but cellphone's audio output has nearly 0.3V. Without another power supply, how can i make my device work? It may be a stupid question but is there any audio amplifier without extra power supply?

    Thanks
     
  2. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    You will not find an amplifier that does not require a power supply.

    What powers your "device" now? Why can't it be used to power a simple gain of 10 preamplifier?
     
  3. scriptr

    Thread Starter New Member

    Sep 17, 2010
    2
    0
    The device is powered with the voltage i get from cellphone's audio output. But it is not enough to make it work

    Isn't there anyway to increase the voltage without any other supply?
     
    Last edited: Sep 17, 2010
  4. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    A small step up transformer with a 1:10 turns ratio will turn your 0.3 volts into 3.0 volts but at 1/10 the current. The primary should have an impedance equal to the headphone impedance. Rectify and filter the secondary's output to power your device. Depending on what rectifier diodes you chose and how you configure them, you may need a turns ratio different than 1:10.The power output of the cellphone will determine the amount of current the rectifier can provide. It will not be very much, maybe not even enough to work with.
     
    Last edited: Sep 17, 2010
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