An H-bridge is an H-shaped circuit with four switching elements and a load in the middle.

In the basic H circuit, there are 4 switching elements, these can be transistors or FETs, 4 diodes, and a load element in the middle. This load element is usually the engine. An example of circuit H is shown in Figure 6.

The main purpose of driving a motor with the H-bridge circuit is to direct the motor with the combination of switching elements on and off.

First, let's assume that switches Q3 and Q2 are closed. The current starts from the power source of the motor and flows over the motor to the ground. Thus, the motor rotates in the specified direction. It can be seen in Figure 7.

In order to ensure the rotation of the motor in the other direction, this time the Q4 and Q1 switching elements must be closed. This time the current flows in the opposite direction and the motor starts to rotate in the opposite direction. It can be seen in Figure 8.