This circuit is from a 1967 documentation. It makes use of varicap and diode tunnel in addition to currently uncommon FET. It serves as a reference.
With this circuit it is possible to keep the current in an LED constant even if the supply voltage...
This circuit was suggested by Motorola in its manual of components for optoelectronics (1987)...
This sensitive circuit can be designed with FETs such as BF245 and MPF102. The sensor is a silicon...