This sensitive bio-monitoring circuit was found in the December 1984 issue of Radio Electronics magazine. The circuit is powered by a 9 V battery and uses a low-impedance headphone output.
Obtained from an English publication, this circuit actually needs a current limiting resistor,...
This circuit has its gain determined by the control DC voltage. The circuit is from a Radio...
This oscillator is a 1950s application of one of the first types of commercial transistors, the...