Problem about the Direction of "pinch-off" in NMOS

[genxium]

I'm learning CMOS course currently, when I review the "pinch-off" today I found that I didn't understand the "direction of pinch" in NMOS, so I went to wikipedia for help: MOSFET - Wikipedia, the free encyclopedia , it's so weird that this graph showed up in the saturation mode part, why the voltage direction is from Source to Drain?

Isn't that in saturation, the Drain voltage should be larger than both Gate and Source (as wikipedia itself stated)? Confused......

 

[dick_freebird]

The graph is showing that the channel is pinched more at
the drain, where the reverse bias against the body is
strongest. I think the voltage arrow shows the direction of
increasing voltage, properly.

 

[genxium]

The graph is showing that the channel is pinched more at
the drain, where the reverse bias against the body is
strongest. I think the voltage arrow shows the direction of
increasing voltage, properly.

Oh...I supposed the convention of arrow is to show the direction of the electric field. Could you tell me more about this? Why does the sharp angle appear in the drain end ? Does the channel consist of electrons?

 

[Jushoraj]

If VGS is held fixed at some point as 8V and VDS is increased from 2V to 5V,the voltage VDG will drop from -6V to -3V and gate will become less and less positive with respect to the drain.Due to that gate to drain voltage inturn reduce the attractive forces for carriers in the induced channel. Because of that reducing channel width at the drain.
Due to that channel will be reduced to that pinchoff point and the saturation is established.

 

[genxium]

Re: Problem about the Direction of "pinch-off" in NMOS

If VGS is held fixed at some point as 8V and VDS is increased from 2V to 5V,the voltage VDG will drop from -6V to -3V and gate will become less and less positive with respect to the drain.Due to that gate to drain voltage inturn reduce the attractive forces for carriers in the induced channel. Because of that reducing channel width at the drain.
Due to that channel will be reduced to that pinchoff point and the saturation is established.

Thanks buddy, this explanation is reasonable !