This sophisticated filter for audio signals was found in Radio Electronics magazine. The frequencies are determined by LC circuits. The circuit has selectivity selected by a switch.
This circuit is from a 1978 optoelectronics manual from Texas Instruments. The transistor can be a...
When no current flows by the base of a transistor it is off and a also an LED in its collector....
This linear characteristic circuit is based on a junction field effect transistor. The FI and BFO...