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.
We found this interesting timer circuit or CMOS timer in a 1988 publication. The circuit is still...
This circuit found in Radio Electronics can be used in games to produce a random pulse train. The...
We found this amplifier with high input impedance and low capacitance, using FET, in a...