The operational amplifier and the sensor used in this National Semiconductor circuit are not common today, but the configuration can be adapted to use current components.
Found in documentation from the 70s, this circuit uses an operational one from that time. It goes for...
This circuit is from an old American publication. It divides a 40 to 60 MHz TTL signal by integer...
This 2004 circuit is based on the ionization effect that occurs in old incandescent lamps with...