This circuit is from 1980s documentation. The maximum operating frequency is 3.5 MHz. The current of the LED can be from 0 to 100 mA. The integrated circuits used are from that time.
We found this circuit in a 1977 factory documentation. The operational amplifiers can be 741 and...
This circuit with regenerative action was found in the June 1986 issue of Radio Electronics...
Equivalent FETs can be used according to the frequency of the crystal which can be up to a few...