What is your concept of pinchoff voltage in an FET?

In a n-channel FET a current will flow from source to drain through the channel when the drain is held positive with respect to the source.

If the gate is negative with respect to the source, the channel is squeezed by an electrostatic field and eventually reduces the current through the channel. If the negative gate voltage is increased, current will stop to flow in the channel, or to put it in another way, the channel will be PINCHED OFF. The gate-source voltage at which channel current becomes zero (where the pinch off occurs) is called the pinch off voltage. It is an electrostatic phenomenon

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RE:

What is your concept of pinchoff voltage in an FET?

An explaination rather than a defenition of Pinchoff Voltage in an FET.

As I understand it, pinch off voltage is the bias voltage - reverse or forward depending on how the FET is designed, normally reverse if I remember correctly - required to stop all current flow from source to drain. In the classical design of the the FET, the Gate is the portion of the FET that bias voltage is applied to and as that voltage changes, the gate either contracts or expands on either side of the channel. The channel is the path from source to drain that current can flow, and is normally oppositely doped silicon with respect to the gate - A P type gate and N type channel for example. The pinch off point is reached when the gates expand to such a degree that they almost touch and block the path from source to drain, thus shutting off the flow of current. The pinch off voltage is more or less unique to each kind or design of FET and can be reached, as I say, with either forward or reverse bias, depending on how the FET is installed/designed/plopped on your desk by a passing Jumbo Jet/etc.

voltage pinch off is actually For a given -VGS any increase in VDS will not cause further increases in drain current. If drain current stops this is VGS OFF which is of the same magnatude as pinch off but opposite polarity voltage eg VGS off = - 5 pinch off = +5 on the transfer characteristic curve.

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This is actually wrong answer .the pinch voltage above defined is actually gate-off voltage. At pinch off voltage drain current become maximum.Drain current is zero at gate-off voltage.

Pinch Off

The answers given here are excellent. But in most cases the current flows from Drain to Source rather than the other way around.

Therefore, when Vgs is incresed so that the Ids is halted, we have channel pinched off.

Pinch-off is the bias point where current ceases. Simple.