It serves as a reference, since today we can have simpler and more compact solutions. This circuit is from an Electronics Experimenter Handbook from 1992. The integrated circuits are from that time.
Other operational amplifiers series, such as the MC34072, MC34074, MC35071, MC35072, MC35074 or...
This circuit with the HA2400 was found in the March 1980 Radio Electronics magazine. The circuit has...
This circuit has two high-impedance inputs. The gain is high and more inputs can be added. Use a...