An H-bridge dc chopper circuit was chosen because
it is the most appropriate for this application. It is simple,
can be driven by TTL control signals, and provides the option
of controlling the motor in reverse, forward, braking, or stopping.
It allows for operation in all four quadrants of the output voltage
output current plane. For this application the H-bridge is used
such that for each motor direction the chopper is very similar
to a basic class A chopper circuit because the forward and reverse
regeneration quadrants are not used.