What is pinch off region of MOSFET?

This phenomenon is known as “pinch-off” and the point where the inversion layer thickness is reduced to zero is called the “pinch-off point.” Pinch-off occurs because, at VSAT, the effective potential between the gate and substrate at the source end of the channel (Veff = VGS) is greater than the potential between the ...
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What is pinch off region and how does it occur?

Pinch off occurs when the the inverted charge near the drain edge under the gate edge becomes zero at the VDS=VDSAT=VGS-Vtn for n-MOSt. Which means one has to put on the drain a voltage equals to the voltage which compensates the excess gate voltage that causes the inversion.
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Why channel is pinched off in MOSFET?

The channel of an enhancement-type MOSFET is said to be pinched off, when the effective gate-to- channel voltage at the drain end becomes less than the threshold voltage, and thus insufficient to maintain a layer of minority carriers across it (needed for the channel to exist).
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What is the pinch off and threshold voltage of mosfets?

The voltage between 10 to 15V is called pinch-off region voltage. It may be any voltage such as 11V or 12V or 12.1V. The pinch-off region is mostly seen in JFET or Junction Field Effect Transistor.
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What is the significance of pinch off voltage?

Pinch off voltage: Pinch off voltage is the drain to source voltage after which the drain to source current becomes almost constant and JFET enters into saturation region and is defined only when gate to source voltage is zero.
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Pinch Off In MOSFETs Simple explanation



What is the function of pinch off?

The pinch-off mold section is designed to cut through the excess extruded material (flash) that extends beyond the part and separate it along the mold parting line.
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What is the difference between pinch off and cut off voltage?

It is a DC voltage applied by the circuit designer. Vgs(off) is the cut off voltage of the JFET which is minimally required to operate it. Thus, Vgs> Vgs(off) means JFET is turned on, but is in the linear region. Pinch off voltage is the Vgs beyond which the JFET enters saturation region.
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How does current flow in pinch off?

The channel gets pinched off near the drain region, this happens because as the VDS increase the drain body depletion region increases(due to reverse bias), now the electrons flowing through the channel are injected into the depletion region at the pinch-off region and are collected in the drain.
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What is meant by saturation region?

Saturation region

This is the region in which transistor tends to behave as a closed switch. The transistor has the effect of its collector and Emitter being shorted. The collector and Emitter currents are maximum in this mode of operation.
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What is channel inversion in MOSFET?

The inversion layer provides a channel through which current can pass between source and drain terminals. Varying the voltage between the gate and body modulates the conductivity of this layer and thereby controls the current flow between drain and source. This is known as enhancement mode.
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How do you calculate pinch off voltage in a MOSFET?

The pinch off of the FET channels occurs at the on set of the saturation of the drain current with the drain to source voltage as has been said and well known, The pinch off condition is at VDS = VDSsat. This is the model equation of the pinch off.
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Why is ID constant after pinching off?

After a certain point (Pinch Off) the drain current becomes constant and will remain constant even if the drain voltage is increased. If we see the physical structure of the device the depletion region will start to increase when the voltage between the drain and source is increased.
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What is the relationship between drain current and pinch off voltage?

At gate-to-source voltage VGS = Vp called the “pinch-off ” voltage, the channel width is reduced to zero because all the free charge has been removed from the channel. Accordingly, for a fixed drain-to-source voltage, the drain current will be a function of the reverse-biasing voltage across the gate junction.
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What is the value of drain current at pinch off condition?

1 Answer. Pinch off voltage is the gate voltage at which the drain current is zero.
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What is VGS off in MOSFET?

VGS,off is the Cutoff Voltage of a FET transistor, which is the voltage necessary to turn the transistor off. For JFETs or depletion MOSFETs, the transistor is normally on, meaning normally conducting current from drain to source.
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What is the difference between VGS and VGS?

Vgs is just the voltage from gate to source (with the red lead of the multimeter on the gate and the black one on the source). Everything else is from context. Vgs(th) is the voltage at which the MOSFET will 'turn on' to some degree (usually not very well turned on).
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What is drain current in MOSFET?

The drain current below threshold voltage is defined as the subthreshold current and varies exponentially with Vgs. The reciprocal of the slope of the log(Ids) vs. Vgs characteristic is defined as the subthreshold slope, S, and is one of the most critical performance metrics for MOSFETs in logic applications.
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What is pinch of voltage in FET?

The Pinch Off Voltage

The Pinch-Off value of the JFET refers to the voltage applied between Drain and Source (with the Gate voltage at zero volts) at which maximum current flows. Operating with the Drain/Source voltage below this value is classed is the "Ohmic Region" as the JFET will act rather like a resistor.
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Why does the drain current at pinch off is essentially zero?

The drain current cannot be completely zero at pinch-off voltage because for drain current to be zero the two depletion layers formed due to the reverse bias must touch each other. But this never happens.
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What does it mean the channel is pinched off?

When we further increase VDS, till the voltage between gate and channel at the drain end to become Vt, i.e. VGS – VDS = Vt, the channel depth at Drain end decreases almost to zero, and the channel is said to be pinched off.
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What is drift region in MOSFET?

A high blocking voltage of a standard power MOSFET requires a thick and low doped epitaxial layer ( -drift region) which causes an increase in the on-resistance. A variety of MOS structures can be used for power MOSFETs.
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Why is inversion important in MOSFET?

When an n-channel MOSFET is in weak inversion, the drain current is determined by diffusion of electrons from the source to the drain. This is because the drift current is negligibly small due to the low lateral electric field and small electron concentration in weak inversion.
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What is weak inversion region in MOSFET?

Subthreshold Region: MOSFET in Weak Inversion. When the surface potential at the source end is sufficient to form an inversion layer but the band bending is less than what is needed to reach strong inversion (i.e., ϕF < Ψs < 2ϕF), the MOSFET is said to operate in weak inversion.
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What is cut off saturation and active region?

In cut off region, both emitter to base and base to collector junction is in the reverse bias and no current flows through the transistor. The transistor acts as an open switch. In the saturation region, both the junctions are in forwarding bias,and the transistor acts as a closed switch.
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