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JFET depletion region question

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ljy4468

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Hi, all

This is a question about JFET.

If Gate, source are at gnd level, and drain voltage is going to higher level,

Then depletion region between drain & gate extends like attatched figure.

And my question is..

If drain voltages goes further higher level,

Is there any possibility that depletion region completely constrict the channel???

Thus no current??
 

This is exactly how Pinch-off is defined you know.....

When the channel is constricted, the transistor is called to be pinched off when the dynamic resistance of the device becomes infinity (ideally) to make no current increase in spite of voltage increase. The dc current cannot be zero, because as the current starts reducing the channel opens up.So it is a dynamic equilibrium when current gets saturated

Any starter's book in FET will detail it to you....
 

Hi, all

This is a question about JFET.

If Gate, source are at gnd level, and drain voltage is going to higher level,

Then depletion region between drain & gate extends like attatched figure.

And my question is..

If drain voltages goes further higher level,

Is there any possibility that depletion region completely constrict the channel???

Thus no current??

by further increase of Vdd (drain voltage) and kept gate and source constant, the depletion region increases and a stage will come when the both ends of the depletion region met at a point ( pinch off ) point. at this point the channel resistance is high enough that it will'nt allow any current through it.. thus the current will be zero through the channel...hope this will help u...KING KHAN
 

JFET Animation : How A JFET Works

**broken link removed**
 

Hi,
When there is no flow of current in the channel due to zerowing the gate voltage the device will go in CUTOFF state and no current will flow in the channel. But raising voltage on DRAIN must not exceed the rated voltage of the device.
 

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