Electrometer or electroscope (CB7375E)

This simple circuit was found in Popular Electronics. It can be built with any JFET. Galvanometers from 100 uA to 1 mA can be used.

Servo Control (CB5941E)
This physical line servo control uses components that are not currently common. The circuit is from...
VHF Modulator (CB5365E)
This circuit is from old American documentation, but the transistor used is still very common...
MAX30004 Integrated Biopotential Detection AFE
August 2017 - This Maxim component, available from Mouser Electronics, is ideal for wearables,...