This circuit shows how to simulate a high-performance diode with two diodes. The circuit is from a 1960s RCA documentation. Modern general-purpose transistors can be used.
We found this active crossover in a Radio Electronics magazine from June 1961. Note the different...
Found in Popular Electronics from the 90s, this circuit serves to indicate the output level of a...
If you are on an old PC that you use for experiments, control or other applications, this circuit is...