function of internal diode of a mosfet??

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prathap205

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why diode is internally connected to the mosfet.and what is its functon???
 

The diode is called a body diode. It is inseparable from the MOSFET by construction.
A NMOS is constructed with n+ diffusion on p-sub.
For discrete NFETs, the p-sub is usually connected to the source, but that still leaves a p-n junction from p-sub to drain diffusion.
That's your body diode.
 

Hi,

The body diode of a typical MOSFET is very slow.

In order to maintain fast switching for high-efficiency, it is necessary to select MOSFETs with fast intrinsic body diodes, or to add additional circuitry to ensure the body diode will never conduct.
 

hi,
the diode is zener diode right???when mosfet switches off it conducts .how it conducts when mosfet is off.

 

Hi,

yes.

This diode conducts when mosfet is off to protect the FET junctions as a general purpose protection(Vds protection).
 

MOSFET is a semiconductor device controllable by the gate signal.The MOSFET device is connected in parallel with an internal diode,then the MOSFET device is reverse biased and no gate signal is applied,this is simulated by an ideal switch controlled by a logical signal with a diode connected in parallel.
 

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