Bootstrap for Switching MOSFET

242

06:17:31

This is an example of how a bootstrap can be used to convert a 5V signal to a signal much stronger than the high voltage at the MOSFETs drain. (Or is it source? Either way, I mean the equivalent of the BJT’s emitter.) That way, the MOSFET can be turned on fully without any voltage drop and without a p-channel one being used. Because of this there is a voltage drop of half a volt at 50 amps. This equates to only 25W dissipation for 50A.

published 8 years ago

hurz

8 years ago

Such a "booster" circuit is interessting in case you want to use cheap and better perfomance N channel mosfets. If you have good P channel onces, its not needed. All the little digital audio amplifier ICs on the market (PAMxyz ), they only have NMOS inside and need for the high side driver a booster cap externaly mounted.

jason9

8 years ago

Interesting. I never knew that. Why can’t they have a PMOS inside? If CMOS is complementary then it has to have both n and p channel MOSFETs. Why can’t the digital audio amplifier have a PMOS output? Can such high power p-channel MOSFETs not be constructed inside those chips for various reasons having to do with the construction/manufacturing processes used to create the chip?

hurz

8 years ago

Right, It can be constructed, but for a much higher price in chip production.

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