This circuit was found in Radio Electronics from the 90s. The CMOS integrated circuit is a PLL not easy to obtain today. The output stage can be exchanged for another one with greater power.
The load controlled by this circuit depends on the triac used. The circuit is from Electronics Now magazine...
This circuit was obtained from a Philips documentation from 1970. It can be built on modern...
We found this preamplifier with 70 dB gain for microphones in American documentation from the...