Preamplifier stage (CB8934E)

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

Triac Triggered by Voltage (CB13371E)
In the figure we show how to trigger a triac for a continuous voltage of the order of 2 V,...
Charge and Discharge Current Sensor (CB5256E)
This 2005 Linear Technology circuit has separate outputs for monitoring the charge and discharge...
Power Semiconductor Test (CB11083E)
This circuit was obtained in a June 1987 magazine Hands-On. It is a circuit that indicates on two...