Question

1) What is meant by knee voltage ?
2) What causes a larger current through a pn-junction diode when forward biased?​

Answer 1

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1 ) The point at which the current rises sharply in the I-V characteristic curve of a pn-junction diode is called the knee point. The voltage corresponding to this point is called the knee voltage

2) When a pn-junction diode is forward biased, the depletion region narrows and consequently the potential barrier is reduced. Hence, the diode has a very low resistance. Therefore, the junction allows a high current to flow across it.

Answer 2

1. The forward voltage at which the current through the PN junction starts increasing rapidly is known as knee voltage.It is also called as cut-in –voltage or threshold voltage. Breakdown voltage: The reverse voltage at which the PN junction breakdown occurs is called as breakdown voltage.
2. This has the effect of increasing or decreasing the effective resistance of the junction itself allowing or blocking current flow through the diode. Then the depletion layer widens with an increase in the application of a reverse voltage and narrows with an increase in the application of a forward voltage.