We found this solid-state relay circuit that can function as a shield in a Radio Electronics magazine from December 1989. The optocoupler is a phototransistor type.
This simple window comparator based on the well-known LM339 was found in the June 1998 issue of...
This circuit makes use of a transconductance operational amplifier. It generates signals with TTL...
This circuit has a traditional configuration often found on this site. The transistor must be...