Opening MOSFET's gate with low voltage PWM

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xmen_xwk

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I have PWM of very low frequency and very low duty cycle. And max voltage comes out are 3.3. But thats not enough to open the MOSFET's gate(IRFP250N). Now I want to amplify the voltage. I do not have op-amp right now. But I tried to use LM393P comparator but its seems too slow. So if I put LED direct to PWM output I can see it blinking but if I put it on output from comparator it stays on. So I assume comparator is not switching fast enough to make it blink.

Now, I'm thinking of using PNP transistor to switch on the MOSFET gate, but I'm not sure which one to buy ? or should I need to try something else ?

PS: I'm learning through internet and still very beginner. So I might have missed something.
 

A gate driver IC like TC427 would be the standard solution. Generally, a gate driver circuit must be able to charge and discharge the gate capacitance with sufficient current to achive the intended switching speed.
 

You said that the PWM signal has a very low frequency (how "low" is it?). Being low (Hz - kHz) there should be no problem with LM393 comparator. If the LED stays on at the comparator's output most probably you didn't set the right triggering level for the comparator (it is too low so the comparator actually thinks that both HIGH/LOW input levels are "high" or something).

Try to choose a different triggering level (and use a hysteresis, too).
 


PWM Frequency : 4Hz
PWM DutyCycle : 2ms
PWM Max Voltage : 3.3V

Yes I will try different triggering level
 

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