An H-bridge circuit arranges four solid-state semiconductor switches (MOSFETs or BJTs) in an 'H' configuration around a central DC motor load, enabling bidirectional rotation from a unipolar power supply. Closing diagonal switches Q1 and Q4 applies positive supply polarity across the armature for forward drive; closing diagonal switches Q2 and Q3 reverses current direction for counter-rotation. Applying Pulse-Width Modulation (PWM) to the gate terminals modulates effective terminal voltage, providing precision control over rotational speed and torque.