How2 Turn On A MOSFET

Focus:

In this article, the author debunks popular misconceptions concerning MOSFET turn on, RDSON and switching speed, explains which datasheet specs are really relevant and how to interpret them. The mechanisms responsible for MOSFET turn-on and turn-off are explained. Mainly, it’s not the threshold voltage (VTH) that matters in turning on the transistor, and turn-on is not an event, but rather a process in which the relevant gate and drain capacitances are charged and discharged as required. Also, the speed with which a modern MOSFET turns on or off is not a simple function of gate charge, especially for superjunction MOSFETs, and RDSON is not relevant below a specified gate voltage. The conclusion nicely summarizes the key points made in this article.

What you’ll learn:

• How to understand the turn-on mechanism of a power MOSFET
• How to understand the factors influencing MOSFET turn-on and turn-off speeds

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Author & Publication:

Sanjay Havanur, Vishay Siliconix, Santa Clara, Calif, How2Power Today, Oct 15 2014

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