In any datasheet of MOSFET, it is mentioned that Gate to Emitter threshold voltage is in the range of 2-4V or little bit higher. But normally we give a voltage about 12-15V. Can any one explain me the reason behind this..?
Gate voltage is direct proportion to switch speed, and is inverse proportion to switch on impedance. You may use a small gate voltage, however, it will reduce switch speed, increase switch on impedance of a MOSFET. Switch speed and switch on impedance may be the most important factors of a MOSFET. You must apply a required gate voltage to realized a switch on impedance given in the datasheet.
Dear Chen
Thank you for your valuable information. In my application I'm using a MOSFET of 1A and i required only in mA. will the switch on impedance will effect much.
Regards
Dear Bharath,
in power electronics or any other application that uses switching devices, it is mandatory to keep the switching losses low, especially at high switching frequency. Typically, "Power" refers to kW.
In your application, power doesn't seem to be the concern, the same might be true for dynamic losses.
So in your case, it seems to be good enough to apply a gate voltage slightly higher than the threshold voltage. Turn-on may be a little slower as compared to using 15V for the gate but my impression is, you're fine.
Anyway your MOSFET seems to be oversized by a factor >100 so if thermal issues are none of your concerns, it seems ok to use a lower gate voltage.