Found in American documentation from 1968, this circuit has an acute cut-off of the frequency to which it is tuned and which depends on RC. Transistors may be modern equivalents of general use.
This configuration uses the 4 gates of a 7401 integrated circuit. The capacitors determine the...
This is a precision half-wave rectifier, suggested by Texas Instruments. Diodes are commonly used,...
This circuit is suggested by National Semiconductor in its 1994 Linear Applications Handbook. The...