BARC 2018 EC-EDC Nuclear Quiz 2

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Question 1

Which of the following statement/s false in case of base-width modulation effect:
a) As V_BE increases, the reverse-bias voltage on the collector-base junction increases, for a given V_CE.
b) Increase in the width of the depletion region of this junction.
c) Decrease in the effective base width W.
d) It will decrease and i_C increases proportionally.

• Aa
• Ba, c
• Cc, d
• Da, c, d

Question 2

In a semi-infinite p-type Si bar, holes are being injected at x=0 such that the steady state excess hole concentration is 2 x 10 ¹⁷ cm^-3. The cross sectional area of the bar is 0.2 cm²,Na= 10¹⁷ cm^-3, τ_p = 10^-10 s and µ_p = 500 cm²/V-s. What is the steady state separation between Ef and Ei at x = 100Å ?

• A1.9878 eV
• B0.4349 eV
• C2.6745 eV
• Dnone of the above

Question 3

In the circuit shown below, the switch was connected to position 1 at t < 0 and at t = 0, it is changed to position 2. Assume that the diode has zero voltage drop and a storage time t_s. For 0 < t ≤t_s, v_R is given by (all in Volts)

• A
• B
• C
• D

Question 4

The circuit using a BJT with β =50 and V_BE = 0.7 V is shown in figure. The base current I_B and collector voltage V_C are respectively

• A43 MA and 11.4 Volts
• B40 MA and 16 Volts
• C45 MA and 11 Volts
• D50 MA and 10 Volts

Question 5

An intrinsic semiconductor bar of Si is doped with donor type impurity to the extent of 1 atom per 10⁸ silicon atoms, then the resistivity of silicon crystal will be
(atomic density of Si crystals = 5 x 10²² atoms/cm³ and μ_n = 1300 cm²N-sec)

• A3.3 Ω-cm
• B5 Ω-cm
• C9.61 Ω-cm
• D10.4 Ω-cm

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