Suitable for clandestine listening and in SMD assembly, this circuit was found in the Radio Eletronics magazine of August 1988. The listening is in headphones and the amplifier is electret.
Found in a1969’s neon lamp documentation, this circuit uses a high voltage transistor. The output...
This circuit is intended to match impedances for observing signals on an oscilloscope. The FET...
This circuit, shown in the figure, consists of a variable gain amplifier with differential input...