How to drive MOSFETs fast

Jul 10, 2009 2 Replies

This might be of use to others that are living in a cave electronically speaking, like me.



Recently spent a day trying to drive MOSFETs fast using bipolars. I'm after a switch time of < 1uSec, and nothing I tried came close. In the end I googled driving mosfets, and up came lots of ads for MOSFET drivers. Turns out these things are a dream solution to the problem. They'll switch a half bridge in a few tens of nanoseconds, with configurable deadtime. They'll handle a bridge with both devices N-channel, and best of all, they'll work with a rail that can be up to hundreds of volts. AND they can be obtained in DIP-8 package. AND, they aren't expensive.


Just make sure you supply them with a low impedance source - good thick power supply rail and good ground. Decoupling write next to the Vcc and GND pins is always advisable - as recommended in the datasheet.

If you want to kick 4A into the gate of a MOSFET, that current has to come from somewhere. If the supply to the chip cannot provide it, your fantastic MOSFET driver will not be as good as advertised..

- Bill Naylor

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Depending on the application they're very likely emitter followers. These can charge Cg very quickly.

Graham

-- due to the hugely increased level of spam please make the obvious adjustment to my email address

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