I am looking for an amplifier

[anasta]

I am looking for a schematic for a preamplifier, for which the amplifier coeficient may be changed by a microcontroller. Is there such an Integrated circuit?

[elp4u]

There are many IC like this, made by Philips, which are controlled by a 2-wire I2C bus, i think they are from the series TDA8ХХХ - check out the Philips web site if you are talking about digitally controlled ICs and you are good in programming.