Amplify cellphone audio output

Thread Starter

scriptr

Joined Sep 17, 2010
2
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
 

Jaguarjoe

Joined Apr 7, 2010
767
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?
 

Thread Starter

scriptr

Joined Sep 17, 2010
2
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?
 
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Jaguarjoe

Joined Apr 7, 2010
767
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.
 
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