What is it?

A Hall Effect transistor is a transducer that response to a magnetic field. There three different types of Hall Effect transistors. Each of these transistors have different responds to the magnetic field.

What does it do?

The first transistor is a proximity switch. When a magnetic field gets close enough to the sensor, it switches on, then off when removing it.

The second Hall Effect transistor is a latch. It reacts by switching on with one pole then holding this state until you switch it off with the other pole. So If the north pole of a magnet turned it on, the south pole of a magnet is then needed to turn it off.

The third hall effect transistor is a proximity sensor. When a magnet approaches the face of the transistor, the output voltage will increase or decrease, depending on which side of the magnet you are using.

How does it work?

The hall effect transistor requires four connections – two to provide current through the device and two to provide the output voltage.

However the negative current supply line and the negative output line are internally connected together.

Thus it becomes a three terminal device that looks similar to a transistor.


It is used in measurement of velocity, rpm, sorting, limit sensing and non-contact current measurements.

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