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MOSFET(metal oxide field effect transistor) please can you tell me why all of mine are short-circuit?They are new! Answered

i have bought 2 mosfets (irf z44v and irf 540) and the drain is live even when the gate is not connected to anything or 0v?

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death defyer

9 years ago

too much power or current

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Plasmana

9 years ago

MOSFET's works differently from transistors. A transistor needs current flowing into (or out) of the base to 'turn on'. A MOSFET needs a small voltage charge at the gate to 'turn on', the gate holds the charge like if it is a capacitor. That is why they stay on when the gate is not connected to anything. I suggest putting a 10k resistor between the gate and the source of the MOSFET to drain the charge from the gate.

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12VPlasmana

Answer 9 years ago

i have just tried this but made no difference.. have you ever had problems with one of two(meaning i may have a bad one)? when i first tried it i connected the gate to the source voltage has this burned it out also how static sensitive are they? also is it energized when the gate is - or+?

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AndyGadget

9 years ago

How are you testing them? The IRF540 has a diode (cathode to drain, anode to source) across it. If you're using a multimeter low resistance check it may well be seeing this. (If you reverse the connections it should be high res with the gate at 0V.)