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I am trying to use an HY1707P MOSFET. I connected a 3W DC bulb load with the drain where I provided 12 V and on the gate I provided 3V. Two separate dc power supply is being used for 12 V and 3V. But the bulb turns on, as usual, with no effect on the gate. I was looking forward to regulating the gate voltage to turn on the bulb. Could you please share why it is not working and what the actual circuit be like? My circuit design is added here. Thank you.

sorry, the diagram needs a change. The negative of the 12V dc power supply will be connected at source (S) in the drawing. Please share a solution to simply run the circuit.

The HY1707 has a Vgs(th) of around 4 Volt. So the voltage at the gate should be at least at 4 V (the current is thus around 1 mA from drain to source), and preferably a little bit more. The 2N7000 would NOT do in this circuit, its maximum ratings are far exceeded. I used it for illustration of the "diagram", not for use in a real circuit.

Thank you, I really appreciate your reply. I have a question: if the gate voltage is 3V, should the light turn on?

I will have follow-up questions, hope you won't mind.

When the datasheet specifies a Vgs(th) from 2 to 4 volt, you MAY fall on a transistor that will refuse to turn on if it is less than 4 Volt. And the spec generally implies that if you could get a tiny current, less than 1 mA, it is "off". So even at 4V, it may turn on, but allowing not a large current.

So, if you are building a single prototype, that should be fine, since you can easily change for another HY1707 as example, since some will be happy to turn "on" for as low as 2 volt at their gate. But if you automatically build thousands of such circuits, automatically, by robots, having one defective circuit in a hundred is probably bad business (since you lose the whole circuit, the other components and the time spent, ... and your reputation of producing reliable stuff).

So, short answer, at 3V, if Vgs(th) is 2 to 4 V? most will work, but some ( one is too many? ) won't.

Thank you. Really appreciate that you made time and replied. Take care.