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MOSFET and PWM and the work region

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lee_lxw

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If VGS < VT working cutoff space
If VGS > VT && VDS < (VGS - VT) working in the region (variable resistance)
If VGS > VT and VDS > (VGS - VT) working in saturated zone
The book should be said so... Should right it.

The first I want to do with PWM control of MOSFET.Through the optical coupling connection.
MOSFET is working in the region?The current ID with VGS changes.? or staturated zone.

The second VGS > VT and VDS < (VGS - VT) working in the region (variable resistance)
VGS > VT and VDS > (VGS - VT) working in saturated zone
The two above, VGS is greater than the VT then D and S conduction, VDS not should equal zero?
8-O
Thank you I don't understand!
 
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goldsmith

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The first I want to do with PWM control of MOSFET.Through the optical coupling connection.
MOSFET is working in the region?The current ID with VGS changes.? or staturated zone.
Hi Lee
It is enough that you know why you're using a mosfet with a PWM command signal ! VGS will be as high as allowed ! ( for usual mosfets 15 volts would be a good choice to turn it on ) thus Id can be as large as infinite ( in theorem ) . because your mosfet is turned on .
I think it is enough to pay attention to this concept that when VGS be higher than threshold voltage it will start conduction but when VGS is around maximum allowed value , your mosfet will be turned on .
Best Wishes
Goldsmith
 

lee_lxw

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Thank you very much! How explain this.
"""The second VGS > VT and VDS < (VGS - VT) working in the region (variable resistance)
VGS > VT and VDS > (VGS - VT) working in saturated zone
The two above, VGS is greater than the VT then D and S conduction, VDS not should equal zero? So which come of VDS > (VGS - VT)"""
 

goldsmith

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Thank you very much! How explain this.
"""The second VGS > VT and VDS < (VGS - VT) working in the region (variable resistance)
VGS > VT and VDS > (VGS - VT) working in saturated zone
The two above, VGS is greater than the VT then D and S conduction, VDS not should equal zero? So which come of VDS > (VGS - VT)"""
Hi Lee
For my opinion you can search in google about this issue !
For instance take a look here , please :
http://en.wikipedia.org/wiki/MOSFET
Best Wishes
Goldsmith
 
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