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[DPRG] All N-channel MOSFET H Bridge a myth ?
Subject: [DPRG] All N-channel MOSFET H Bridge a myth ?
From: Rick Mann
rmann at latencyzero.com
Date: Sun Oct 8 13:00:33 CDT 2006
On Oct 8, 2006, at 09:10 , Vimal Shankar wrote:
> Is an all N-channel MOSFET H Bridge a myth ?
Not at all. N-channel FETs generally handle more current than their P-
channel counterparts, and so H-bridges made from them are popular.
However, you need to drive the high-side FETs well above Vdd, because
the FET source can be close to Vdd when it's on. The higher Vgs is,
the more "on" it is, and the less power you'll dissipate through it.
Because of that, there are numerous drive ICs available. Check out
International Rectifier's MOSFET Gate Drive chips (MGD). For sub-100%
duty cycles, they provide the voltage boost you need, and they also
provide logic to prevent both the high- and low-side FETs from being
turned on together.
--
Rick
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