Audio Signal Clamping

[Shivendra Mishra]

Hello folks!:-D
I was trying to connect my microphone to Analog comparator (AVR controller) for finding out frquencey of, whatever i speak.
The output of mic after amplification sounds good on speaker but when i checked on a scope it is showing me a signal with -2.5V to +2.5V amplitude; Which is not accepted over the analog comparator (Accepts 0 to 5V).
I made a small clamping circuit with 1uf capacitor, 1k resistance and a diode; but it doesn't really push the signal positive side.

Any other idea, how should i do this ?

Thanks in advance!

 

[Audioguru]

Use an NPN emitter-follower transistor with a +5.6V supply and its base biased at +3.1V. Use an input coupling capacitor to feed the -2.5V to +2.5V signal to its base. Use a suitable value for its emitter resistor then its emitter output will idle at +2.5V and audio will cause its emitter output to swing maximums of 0V to +5V.

 

[Shivendra Mishra]

Hello,

I experimented as per you said. I don't see any signal coming out on Rl. And my 3.1V battery was too much heated and reached to 2v. I'm not much experienced with analog circuit . Any clue where did i went wrong? I feeded 2KHz signal as input to this circuit.
Here is my circuit:

 

[Audioguru]

What you did wrong is to not learn anything about transistors. Nothing in your circuit will heat your 3.1V battery.
A transistor has a DC base current. Your circuit has the base floating at DC with nothing providing the base current.

I changed your 2N2222 high current switching transistor to a 2N3904 linear transistor that has more detailed spec's.
I provided DC base current with two added resistors and calculated their values using Ohm's Law.