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 is a typical amplifier circuit for a commercial tape recorder from 1968. The circuit has an...
This circuit functions as a variable capacitor controlled by a potentiometer, multiplying the...
This differentiator for the positive front of the input signal can be elaborated based on any...