GATE EC 2022: EDC Quiz 9 for ESE & GATE EC Exams

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 ϵ_r = 11.7)

The built-in potential barrier, V_bi, 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 ϵ_r = 11.7)

What will be the distances x_n and x_p 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 N_d = 10¹⁵ cm^-3 and N_a = 0. The equilibrium recombination rate is R_p0 = 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 N_d = 10¹⁵ cm^-3 and N_a = 0. The equilibrium recombination rate is R_p0 = 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 D_n = 20 cm²/s, n_B0 = 10⁴ cm^-3, x_B = 1 μm, A_BE = 10^-4 cm². What will be the collector current (in μA) for VBE = 0.5 V?