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# GATE EC 2022: EDC 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 2

Direction: Consider the impurity doping profile in a silicon pn junction as shown in figure. Assume that zero voltage is applied to the pn junction. (For Si, relative permittivity is ϵr = 11.7)

The built-in potential barrier, Vbi, is

Question 3

Direction: Consider the impurity doping profile in a silicon pn junction as shown in figure. Assume that zero voltage is applied to the pn junction. (For Si, relative permittivity is ϵr = 11.7)

What will be the distances xn and xp that the space charge region extends into the n and p-regions respectively (in μm)?

Question 4

In a silicon semiconductor material at T = 300 K, the doping concentrations are Nd = 1015 cm-3 and Na = 0. The equilibrium recombination rate is Rp0 = 1011 cm-3 –s-1. A uniform generation rate produces an excess-carrier concentration of δn = δp = 1014 cm-3.

The excess-carrier lifetime is _ _ _ _ _× 10-7 s.

Question 5

In a silicon semiconductor material at T = 300 K, the doping concentrations are Nd = 1015 cm-3 and Na = 0. The equilibrium recombination rate is Rp0 = 1011 cm-3 –s-1. A uniform generation rate produces an excess-carrier concentration of δn = δp = 1014 cm-3.

By _ _ _ _ _× 109 factor does the total recombination rate increase ?

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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