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Dec3-09, 06:20 PM   #4
 

Why does a MOSFET heat up with slow rise/fall times at gate?


Quote by saad87 View Post
Thank you!

Does this phenomena occur in BJTs too? If so, why are inverter BJTs circuits used to improve the rise/fall times of the waveform?

In my case, I was recommended that I should insert a BJT inverter between the output of the comparator and the input of the MOSFET. There is a resistor connected between the collector and power supply. This resistor ends up making a RC circuit with the input capacitance of the MOSFET and due to a time constant of 1uS, the rise/fall time is much faster.

Does this make sense?

Also, do slow rise/fall times affect the switch speed of a transistor?
Exactly, an inverter circuit would be able to source/sink more current than the comperator, allowing the mosfet to switch on and off more quickly, meaning that it will be in the linear range for a shorter amount of time, thus reducing switching losses.