Preamplifier stage (CB8934E)

This circuit is from a 90s Popular Electronics. It appears elsewhere on this site. Q1 can be any general purpose transistor.

Nanoammeter (CB12009E)
This circuit allows the measurement of very weak currents indicated on an analog instrument or...
Preamplifier with tone control (CB9517E)
Found in National Semionductor documentation this circuit combines a tone control with an...
RF Generator (CB7424E)
Found in a 73 magazine from the 1980s, this circuit generates signals from 3.2 to 22 MHz. FETs can be...