This circuit was obtained from a 1965 Radio Electronics. The semiconductors used admit modern equivalents. The high voltage coil is an automobile ignition coil.
This circuit can be used as an optical switch or photosensor to excite TTL logic. The transistor can be...
This circuit was found in a Popular Electronics of the 90s. The output amplitude will be between...
This 80's Exar circuit has a carrier detector for frequencies up to 500 kHz. The circuit uses a...