Telephone Audio Amplifier

[MHKN]

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.

 

[metal]

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

 

[yeechyan]

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.

 

[metal]

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

 

[batdin]

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

 

[e_eja]

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