100 Hz Second Order High Pass Filter (CB25815E)

This filter with the 741 op amp was found in the February 1995 Electronics Now magazine. The power supply must be dual.

Biestable Touch Switch (CB10246E)
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
Intercom LM384 (CB7033E)
This circuit was obtained in an old Elektor. It is a reference, since the integrated products of the...
Physiological Control (CB19188E)
This circuit was found in a European technical documentation from 1991. It is a circuit that must...