Hello I'm using this schema but my problem is that the mosfet is overheating can you ell what exactly the problem

 

Any transistor operating in the linear region is going to act like a resistor and will get hot.
What size of heat sink is the transistor mounted?

 

It looks as though your transistor is turned full on, and will be a short circuit to ground. What's this circuit mean to be doing, anyway?

 

I'm not using heatsink

Any transistor operating in the linear region is going to act like a resistor and will get hot.
What size of heat sink is the transistor mounted?

I'not using a heat sink

 

hi phys,
What is the resistance and inductance of the coil, also confirm the value of the input capacitor.
Is that 5Vrms or 5V peak.?
E

 

I'm not using heatsink

I'not using a heat sink

Then mount it on a very large heat sink. You need to dissipate about 10W.

 

Hi phys,
This is what LTSpice shows, you may have a component or wiring fault.
I have assumed a1H inductance.
The plot looks OK [ Corrected]
E

 

I calculate the inductance now L=18nH

Then, basically, your load is a 5.5Ω resistor.

Bob

 

hi phys,
This is with 18nH inductor.
E

 

The magnetic field at 50Hz in the extremely low inductance will be very close to zero. We do not know if the input signal is 5Vp-p when many IRF540 Mosfets do nothing or if the input is 5V peak when some sensitive IRF540 Mosfets produce a squarewave output.

 

If your inductor is 5ohms and your power supply is 7v, then about 1.4amps is going into the mosfet. 7v isn't turning it all the way on so the mosfet is likely a bit over 0.2 ohms to 0.5 ohms load. At 1.4 amps, that is 0.35 to 0.7 watts.
Your MOSFET will definitely be hot to the touch and possibly burn you. It may not be too hot per the datasheet. Please define "overheating". Hot or damaged?

also, there are many modern MOSFETs that. Will be a few milliohms when the gate is at 5-7V. No heat there to worry about.

 

Maybe the very low value "inductor" shown in the image measures 0.5 ohms like a piece of wire and the meter leads measure 5 ohms?
There is a sinewave input. Does he want a sinewave output?

 

The original schematic does not show exactly where the tiny inductance is connected:

 

John P already pointed out the basic problem, you can't make the mosfet start with a turn on status, R1 should be Grounded.

 

I think it would be difficult to wind a wire with 5.5 Ω into an inductor that is only 18nH unless it is a special high resistance wire.

As an example, 1 turn 1cm in diameter air core is 20 nH

Bob

 

John P already pointed out the basic problem, you can't make the mosfet start with a turn on status, R1 should be Grounded.

Then the Mosfet would rectify the signal and produce only a little of the top part of the waveform.

 

Then the Mosfet would rectify the signal and produce only a little of the top part of the waveform.

Thanks for your mentioned, I'm too digitalized to think about the circuit and forget the signal is a sinewave, but if you choose the Vgs(on)=2.5V then maybe the results doesn't that bad.

 

And what do you expect it to do?

Bob

 

And what do you expect it to do?

Bob

It seems to be doing what it should do, not what he wants it too. Makes little or no sense.

 

My schematic is like that

The 47uF capacitor polarity is backwards and its value is much higher than is needed for audio frequencies.
The Mosfet will rectify the signal then the output is pulsing halves of a sinewave.
The 10k resistor will turn on the Mosfet when there is no input signal which might waste a lot of power and heat the inductor.