This amplifier with gain control was obtained in a documentation from Signetics of the 80's. Transistors are of power and operational amplifiers are not common nowadays.
November 2016 - Maxim's MAX30003, an Analog Front End (AFE) for biopotentials with clinical grade...
This receiver was found in the Radio Electronics magazine of March 1953. It tunes to the medium wave...
Audio signals can be produced by this circuit. Frequency range is determined by C1 and adjusted by...