Electronic Control for DC Motors Using Discrete Bridge Circuits

In this article, motor means a permanent-magnet, direct-current (DC) motor of
the sort used in toys, models, cordless tools, and robots. These motors are
particularly versatile because both their speed and direction can be readily
controlled; speed by the voltage or duty cycle of their power supply, and
direction by its polarity. DC motors also work as generators. Since generators slow down when they are heavily loaded, DC motors can be electronically
braked. Control means at least on/off and direction control. Variable speed and braking are also desirable.