Modulated light receiver (CB21790E)

We found this circuit in a Mullard manual from 1960. The transistor is a phototransistor of the time. The gain is 3 dB.

Debouncer (CB20546E)
This anti-ringing circuit was found in an English documentation from 1996. The integrated circuit is...
Higher gain stage (CB25057E)
The figure shows how to increase the gain of the amplifier stage of the previous circuit. The...
Voltage Controlled Function Generator (CB18882E)
This circuit uses unusual operational amplifiers, but equivalents can be tried. FETs can also be...