Picoammeter (CB6192E)

This circuit was found in a 1980s Intersil documentation. The integrated circuit used is not common today. The power supply must be symmetrical.

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Relaxation Oscillator with common Transistors (CB10211E)
We can say that this circuit is equivalent to a unijunction transistor in the relaxation...
Loop Antenna Q Multiplier (CB13648E)
I found this circuit in a documentation for radio amateurs from 1975. The FET could be the BF245....
Logic test with sound (CB25389E)
This circuit has visual and audible status indication using an oscillator. The circuit is from a...