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Why there is an inherent diode inside the MOSFET symbol?

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Jebakumar Samuel

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Hi,
I need to know why there is a inherent diode inside the MOSFET symbol. Is it useful in any ways? how the diode is formed?
 

Re: MOSFET

Hi Jebakumar Samuel,

As I remember the diode is an artifact of the basic design on the wafer level. I think it takes very little extra effort to produce it in the device. I have included a couple pages from a power electronic books that might be helpful to you.

Regards

dfullmer
 
Re: MOSFET

Jebakumar Samuel said:
Hi,
I need to know why there is a inherent diode inside the MOSFET symbol. Is it useful in any ways? how the diode is formed?
Click to expand...

It's a socalled damping diode, and is usually there to protect the gate.
 

Re: MOSFET

Yes dfullmer is right - the body diode is an intrinsic characteristic of the MOSFET. The technical pages are not so clear in pointing out that the body diode is VERY USEFUL in the case of a half-bridge or full-bridge switching circuit driving a load with some amount of inductance. This is very typical of servo-motor drive applications. In the old days before MOSFETs, BJT devices were used, and high-speed diodes had to be added across the collector-to-emitter to protect the BJT's from overvoltage failue during deadtime due to thier inability to conduct current in the reverse direction.

I also recommend the International Rectifier website http://www.irf.com as a good source of basic information
 

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