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H Bridge Motor Control Circuits

H Bridge Motor Control Circuits

This page features H-Bridge circuits used for controlling direct current motors. Several designs are shown using both CMOS and Bi-Polar power devices.
Comparator Controlled H-Bridge Circuits (LM311)

The next two circuits are simple Bi-Polar H-Bridge circuits. The bridges are controlled by a pair of LM311 voltage Comparators.

The LM311 Voltage Comparator has several unique features, one of which is an output transistor with an open emitter as well as the typical open collector. This allows the output transistor of the comparator to sit between the bases of the power transistors.


The LM311 Voltage Comparator also has a STROBE input that will turn off the output regardless of input conditions.

The circuit is shown in two configurations. The first is a typical two input bridge. The second circuit has a single – duplex input that would be used for model railroad “DCC” control applications.

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