# NEET Physics Semiconductor Electronics Questions Solved

The junction diode in the following circuit requires a minimum current of 1 mA to be above the knee point (0.7 V) of its I-V characteristic curve. The voltage across the diode is independent of current above the knee point. If ${\mathrm{V}}_{\mathrm{B}}$ = 5 V, then the maximum value of R so that the voltage is above the knee point, will be

(a) 4.3 k$\mathrm{\Omega }$                 (b) 860 k$\mathrm{\Omega }$

(c) 4.3 $\mathrm{\Omega }$                   (d) 860 $\mathrm{\Omega }$

(a) At knee point voltage across the diode is 0.7V.

Hence voltage across resistance R is 5 – 0.7 = 4.3 V.
$⇒$ using V = iR $⇒$ 4.3 = 1 $×$ ${10}^{-3}$$×$  R$⇒$  R = 4.3 k$\mathrm{\Omega }$.

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