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# GATE EC 2022: Electronic Devices Quiz 9

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Question 1

An npn bipolar junction transistor (BJT) is operating in the active region. If the reverse bias across the base – collector junction is increased, then

Question 2Multiple Correct Options

The built-in-potential profile in the depletion region of a p-n junction in equilibrium is shown in the figure. The depletion region width is 1 μm. Which of the following statements is/are true?

Question 3

In a silicon p–n junction, the variation of the hole concentration in the space charge region is shown in the figure below, where the hole concentration changes from PPO to Pno aver the space charge layer width The hole diffusion constant in the space charge region is 6.5 cm2/sec. Then the hole diffusion current density JP is _______ kA/cm2.
(Note: Depletion width in the p–side, xp = 1 and in the n–side, xn = 2 )

Question 4

At temperature T = 300 K, an n-type silicon contains donor concentration, ND = 1014 cm–3 and intrinsic carrier concentration ղi = 1.5 × 10–10 cm–3. Assume minority carrier lifetime of holes is po = 10 μsec. Then lifetime of majority carrier electron is _____.

Question 5

In an n–type semiconductor, the electron concentration (no) = 1015 cm–3 and the intrinsic carrier concentration (ni) is 1010 cm–3. The mean life time of minority carriers is 10–6 sec. The steady state excess hole concentration due to constant light illumination is dp = 4 × 105 cm–3. The steady state electron – hole recombination rate is __________.

Question 6

The parameters in the base region of an npn bipolar transistor are Dn = 20 cm2/s, nB0 = 104 cm-3, xB = 1 μm, ABE = 10-4 cm2. What will be the collector current (in μA) for VBE = 0.5 V?
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