This circuit was published in an article in Radio Electronics magazine in October 1988. It uses components that are still common today, except for the sensor, which is a special type from that time.
This circuit from an old documentation uses an optocoupler to control the feedback. FET is...
We found this circuit in a publication for radio amateurs in 1974. The bipolar transistors can be...
This circuit was found in a documentation for radio amateurs from the 70s. The integrated circuits...