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Mosfet mas Vgs rating.

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biprangshu

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Why there is max Vgs (usually +-20v) rating for power mosfet? Does it also apply to Vgd? If it applies then how max Vds rating is very high compare to Vgs , bcoz (considering NMOS) with Gate Source sorted Vgd will be really high if it is operating at max Vds?
 

Hi,

Does it also apply to Vgd?
Click to expand...
No. V_GS is the voltage between gate and source of a MOSFET. It has nothing to do with drain.

Gate is the control path, with it´s own isolation barrier and isolation voltage referenced to source.

Drain is the power path, with it´s own isolation barrier and isolation voltage referenced to source.

***
I recommend to read about MOSFET construction. Use wikipedia or similar.

Klaus
 

As per the construction it is important to note Source and Drain is reversible ( unless body is connected to the source). The Max Vgs ratings is most likely the safe limit voltage of gate Oxide breakdown. If it is so then a high Vgd also can make a break down of the oxide. Thats why I asked does this applies to Vgd too ?
 

Hi,

As per the construction it is important to note Source and Drain is reversible
Click to expand...

--> this is true for a symmetrically constructed JFET (only).
Where did you find information that this is true for MOSFETs also? Please show.

Klaus
 

I am CMOS VLSI circuit design engineer. We dont care source and drain connection as long as it is a 4 terminal device and body is connected to required potential, for our product development. that is NMOS body to vss and PMOS body to VDD. In layout also one does not need to care for source / drain separately.

leaving this apart, do you have any idea what the max Vgs represents, in other words what will happen if someone exceeds max Vgs. as per my knowledge gate oxide breakdown will occur. As per the given image Gate and drain separated by gate oxide only , therefore I think the same breakdown can occur in drain side oxide also, hence a max Vgd rating is also required if we are specifying max Vgs.

MOSFET-BLOCK-DIAGRAM.png

-biprangshu saha
 

That's no power MOSFET chip.

If you want to know the voltage ratings for ASIC technologies, refer to the PDK specifications.
 
Thanks to all of you for clearing my confusion. I came to know that power mosfet construction is different than Normal mosfet.

-thanks
biprangshu saha
 

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