Using an LDR as a sensor, this circuit is from the Radio Electronics magazine of December 1984. The operational amplifier is the 741 and the source must be symmetrical.
This circuit is from a 90s Popular Electronics. It appears elsewhere on this site. Q1 can be any...
This circuit works as a booster operating with signals from 1 to 30MHz. The gain is between 1 and...
This timer circuit was found in a 1980s American documentation. Transistors and SCR support modern...