This is the traditional H bridge configuration for motors. The circuit is for currents up to 500 mA, but with higher power transistors such as the TIP31 motors up to 2 A can be controlled.
To operate in a harmonic of the crystal frequency, tuned to a trimmer in the resonant circuit of...
This amplifier for recording heads was found in a Radio Electronics from September 1963. The...
This circuit is from the 1983 Intersil Databook. The circuit operates on 5 V power and has a...