popa
I have a condensor microphone element from Radioshack and i was wondering what 100x oamp I could use with it to feed signals to the arduino, I was thinking the opamp from TI would work (http://www.ti.com/lit/ds/symlink/opa344.pdf).
thank you,
popa
Do you mean an electret mic ? A small mic of 1 to 10 dollars that requires 5V or 9V ?
A real condensor microphone is used in a studio and costs hundred(s) of dollars and needs often 12 to 48V phantom power.
An electrec mic is not very good, and the Arduino is not very well with audio. So you don't have to use a precision opamp, a single transistor will do.
Some sellers call an electret mic a "electret condensor mic" or even a "condenser mic". That is just to make that cheap microphone element look better, but I think that is wrong, bad, illegal, and so on.
Just about any op-amp will do. This is good chioce because it's a "rail to rail" op-amp and the output will get closer to ground & 5V than a "normal" op-amp (assuming you power it from +5V). If you don't run the op-amp from dual (positive & negative) power supplies, you'll need to bias it at half the supply voltage.
The electret mic element needs to be powered/biased too, but you'll need a capacitor between the mic and the amplifier to isolate the power/bias. Normally, you'd filter-out the DC bias with a capacitor at the amp's output, but the Arduino can't accept negative voltages, so it's usually biased at 2.5V also.
Search for a schematic for how to "power" an electret condenser. (I think it just takes a resistor and a capacitor, plus a small DC voltage of course.)
what 100x oamp...
The gain depends on the resistor values, not the particular op-amp. A gain of 100 is probably a good starting point but you'll have to experiment with the gain (depending on the sensitivity of the mic and the loudness of the sound) and you'll probably need a volume control pot between the mic and the amplifier. Or,you can use a pot in the op-amp's feedback resistor for variable gain.
An electrec mic is not very good, and the Arduino is not very well with audio. So you don't have to use a precision opamp, a single transistor will do.
It's a LOT EASIER to build a linear amplifier with an op-amp! You CAN build a good quality amplifier with discrete transistors, but a gain of 100 is "pushing-it" for a single transistor design.
Some sellers call an electret mic a "electret condensor mic" or even a "condenser mic". That is just to make that cheap microphone element look better, but I think that is wrong, bad, illegal, and so on.
Not always... [u]Here[/u] is an example of a good electret condenser mic.
I was thinking of using this mic from radioShack (http://www.radioshack.com/electret-microphone-element-with-leads/2700092.html#prefn1=productType&prefv1=Microphone+elements&start=1)
popa
[u]Here[/u] is some information about wiring/powering electret elements. You'll still need an op-amp gain stage.
If you want to make things easier, [u]this circuit board[/u] has a mic and all of the required circuitry, including the amplifier and biasing circuit. (But it has fixed gain, which could be an issue.)