This NEC commercial amplifier was manufactured in Japan in the 1960s. The circuit uses 4 transistors from the time and was powered by a 9 V battery voltage formed by large batteries.
We found this circuit with an operational transconductance amplifier in the Motorola Linear...
Originally the circuit in the figure is indicated by National for the control of an electronic car injection...
This small two-transistor amplifier was found in the April 1994 issue of Electronics Now magazine. This...