Integrator with JFET (CB6229E)

This circuit was found in an 80s National Semiconductor documentation. The configuration holds true for modern JFETs.

Darlington Touch Switch (CB7191E)
This circuit is from 1968 General Electric documentation. It can certainly be adapted for any...
Capacitor Tester (CB4391E)
This tester from a 1960 magazine is only for capacitors with insulation voltages above 200 V (110...
Unijunction Telegraphy Oscillator (CB12283E)
Found in a 1991 publication this circuit can be assembled with more modern components. We can use...