Suggested by National Semiconductor in documentation from the 90s, this circuit uses a switched regulator of the time. The circuit is suitable for NiCad battery charges.
When the sensor, an ordinary photo-transistor, receives light, the relay closes its contacts. The...
This circuit consists of a bass filter that can be used as a subwoofer in a sound system. The...
This circuit has a traditional configuration often found on this site. The transistor must be...