This interesting sensor for RF signals was found in an article in the June 1989 Radio Electronics magazine. It is a field strength meter with an LED bargraph indicator.
This circuit is found in the Italian magazine Radio Elettronica, August 1975 issue. There is a...
This signal follower is from a 1970's documentation. So it uses the traditional configuration at the time...
We find this circuit in an old American documentation from the 80's. The integrated is from the...