We found this circuit in a 1986 documentation. It uses only LEDs, batteries, resistors and the power supply which can consist of 4 batteries or a 9V battery. The basic circuit uses two-color LEDs.
This two-stage circuit has a voltage gain of 100 times, with a high input impedance. The circuit is...
Four amplifiers are used in this circuit, which uses a magnetic pickup to obtain the pulses whose...
This simple circuit was obtained in a Portuguese publication in 1979 but can be easily assembled with...