In the figure we have the way to obtain 500 gain from a FET. FETs can be BF245 or MPF102. The circuit is from the 1977 National Semiconductor FET Data Book. Power supply depends on the application.
This instrument was obtained in a documentation for radio amateurs of 1976. The circuit measures...
This circuit decodes FSK signals with frequencies of 1070 and 1270 Hz and can be used in data...
We found this circuit for guitar training in an English documentation from 1989. The components are from...