Both the operational amplifier and the diodes admit equivalents in this circuit suggested by National Semiconductor. The power source must be symmetrical, and the circuit curve resembles an ideal diode.
This circuit with LDR and neon lamp has its operating frequency given by the light. The circuit is from...
Found in American documentation from the 90s, this circuit can be used as a shield with the...
This tone recognizer circuit that relies on R5 and C1 was found in the December 1994 issue of...