# Confusion regarding pinch off voltage in a JFET

by smatik
Tags: confusion, jfet, pich, pinch, voltage
 P: 14 I can't figure out what actually is the Pich-off voltage of a JFET. I basically have confusion between these two definitions:Pinch off voltage is that gate source voltage at which there is no drain-source current Pinch of voltage is that 'Drain-Source' voltage after which the drain source current becomes almost constant(saturates). If there is some other accurate definition for pinch off voltage,Please tell me. Also i want to ask that what is pinch off region? Thanks
 P: 409 Here you find answer what is pinch off region. http://www.electronics-tutorials.ws/...or/tran_5.html So the proper definition of a Pich-off voltage is Pinch of voltage is that 'Drain-Source' voltage after which the drain source current becomes almost constant(saturates). And for n-channel JFET Pich-off voltage is positive. But because Vgs(off) (the gate source voltage at which there is no drain-source current) voltage is negative and by accident equal to the magnitude of the pinch off voltage. Hence: |Vgs(off)| = |Vp| the magnitude of the pinch off voltage is equal to Vgs(off). And this is why we can say that |Vp| = |Vgs(off)| but in the same time Vp is a saturation voltage. But the only difference is the minus sign. Because Vgs(off) is negative but Vp is positive.

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