Found in a 1992 book, this circuit is intended for operation with audio signals. Equivalent operational amplifiers can be used. The optical coupler is an unusual type today.
This circuit consists of a traditional version amplifier with complementary output transistors...
This circuit is from a manual of linear integrated circuits of the 80s. The operational is of the...
Also suitable for use as a noisy alarm, this Morse Code or telegraph practice oscillator was found...