This filter for frequencies from 300 Hz to 3.4 kHz was found in the February 1995 Radio Electronics magazine. Other operational amplifiers can be experimented, and the source must be dual.
This 1987 circuit has a very interesting concept. It powers a second set of rhythmic lights from...
This circuit was found in an Electronic Design from the 80's. It shows how to use a MOSFET driver with...
We find this circuit in an American documentation from the 80's. The circuit has the coil given by the...