This circuit rejects frequencies around 1 kHz and can be adjusted using C1. Equivalent operational amplifiers can be used, and the power supply must be symmetrical.
This circuit is from an October 1963 Radio Electroncs. It uses a single 2N18383 transistor and a...
We found this circuit in a 1972 RCA technical documentation. The comparator can be any type and C1...
Found in a 1970 EEE this circuit emulates a zener diode whose voltage can be set to R2. Power...