This circuit was found in a 1968 Motorola documentation. The circuit can be implemented with virtually any photo transistor and general-purpose transistor.
This circuit was found in Motorola documentation from the 1980s. PUTs are not common components...
This low distortion circuit was found in a 1964 Electronic Design. The transistor admits...
This circuit is based on an uncommon Texas component today, as found in an American 1980s...