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First time asking a question here. I have a Hall sensor A3144 that goes to low when a magnet activates it. So I can use a magnet with it to complete a circuit, say, connecting the output to a red LED to 5V.

But I want the output to connect to the gate of a MOSFET so I can turn on an electromagnet with higher voltage using drain and source. For testing, I'm using a green LED instead of an electromagnet.

The problem is that I get the opposite of what I want. With no magnet, the Hall sensor outputs a small voltage (in this case around 1 volt), and the MOSFET receives this small voltage to the gate, and the green LED turns on. With a magnet, the Hall sensor drops to 0 volts and the green LED turns off.

I need the opposite to happen. I need the green LED (or the electromagnet) to turn on when the Hall sensor detects a magnet and be off otherwise. Can you help me do this?

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    \$\begingroup\$ Welcome to EE.SE. A schematic is better than words. You can add one in using the CircuitLab button on the editor toolbar. Double-click a component to edit its properties. 'R' = rotate, 'H' = horizontal flip. 'V' = vertical flip. Note that when you use the CircuitLab button on the editor toolbar and "Save and Insert" on the editor an editable schematic is saved in your post. That makes it easy for us to copy and edit in our answers. You don't need a CircuitLab account, no screengrabs, no image uploads, no background grid. Add in a link to the Hall sensor datasheet. \$\endgroup\$ – Transistor Aug 18 '20 at 17:46
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    \$\begingroup\$ @TimWescott More than A3144? \$\endgroup\$ – Wade Martin Aug 18 '20 at 18:04
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    \$\begingroup\$ You could use a P-channel MOSFET and drive the LED from the high side. \$\endgroup\$ – Cristobol Polychronopolis Aug 18 '20 at 18:07
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    \$\begingroup\$ DigiKey lists over 1500 unique Hall effect switches in their catalog. So yes, more than one. \$\endgroup\$ – TimWescott Aug 18 '20 at 18:11
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    \$\begingroup\$ If you are indeed using the A3144, could you please edit your question with a link to a datasheet -- here's the one I found: allegromicro.com/-/media/files/datasheets/… \$\endgroup\$ – TimWescott Aug 18 '20 at 18:12
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As @CristobolPolychronopolis suggested, using a P-channel MOSFET instead of an N-channel MOSFET to drive the LED from the high side worked. Many thanks, Cristobol!

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