I found this circuit in a documentation for radio amateurs from 1975. The FET could be the BF245. The circuit works in the range of 40, 80 and 160 meters of radio amateurs.
This series LED circuit was found in the February 1992 issue of Radio Electronics magazine. The...
We found this circuit in the Linear Applications Handbook by National Semiconductor. The circuit uses...
The noise comes from the PN junction of a common silicon diode. Since no gain is given by the...