Multipurpose temperature control (CB21368E)

This circuit was found in a 1967 RCA SCR manual. It uses period components that can be replaced with modern equivalents.

Sound operated switch (CB9214E)
This circuit was found in a Hands On Electronics from the 90s. The microphone is a small 75-ohm...
FET Stage with Gate Offset Adjustment (CB26251E)
This JFET amplifier stage was found in the Encyclopedia of Electronic Circuits Volume 5 from 1995....
Optimized Operational (CB15106E)
To obtain more output power from an operational amplifier, we can use a transistor, as shown in...