Telephone Audio Amplifier

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Hi
I want to make a Audio Amplifier to increase the sound of telephone speaker and make a Telephone Microphone Audio Preamplifier.I want thses circuit's power supply was gotten from Telephone Line(We haven't another external power supply).If you know a link that guid me or know anything about it ,please tell it.
 

Hello

You can use LM386, I don't think it will need lots of power if you use it with 8 Ω, or 16 Ω.

Go to national homepage to download the datasheets.

Regards
 

Even a 741 can do the job. Do you mean you're taking the power from the telephone line? The line voltage at idle is about 60V. Do take note on that.
 

Hello

Regarding the variable telephone power supply, you can use LM783, this can stand high voltages at the input , and enough input/output differences without breaking down.

Regards
 

Bear in mind that when the line is busy,the voltage across it is between 5 and 10V.
 

the voltage is distinguished by on hook stae and off-hook state, when in on hook state the voltage between 40-60 Vdc, and when off-hook the voltage betwen 9-12 Vdc, the problem is the current delvered from central should be known in order to drive any op-amp or transistor amplifier and finally loudspeaker
 

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