Electrical Engineering Answers

(3) Which of the following statements is (are) true about reverse bias breakdown due 

to impact ionization and Zener tunneling? ( ).

A. Tunneling breakdown generally occurs at lower voltages than impact ionization. 

B. Tunneling generally has a weaker temperature dependence that impact ionization. 

C. Significant tunneling only occurs when the junction is heavily doped. 

D. All of the above. 

(4) Consider an abrupt PN junction. Let Vbi be the built-in potential of this junction and 

VR be the applied reverse bias. If the junction capacitance (Cj) is 1 pF for Vbi + VR = 

1 V, then for Vbi + VR = 4 V, Cj will be ( ).

A. 4 pF B. 2 pF C. 0.25 pF D. 0.5 pF 

1. Multiple Choice (Choose the ONE answer that best fits the question/statement.) 

(1) When the “n­factor” of a diode ID = I0(eqV/nkT −1) is 2 at low forward bias voltages, 

what do we suspect? ( ).

A. That the current is dominated by high level injection in the lightly doped, quasi-

neutral region. 

B. That the current is dominated Zener tunneling 

C. That the current is dominated by recombination in the space charge region. 

D. That the current is dominated by generation in the space charge region. 

(2) How does series resistance affect on diode characteristic? ( ). 

A. It leads to the sharp increase of the current 

B. The direct current, depending on the voltage, increases slower than exponential 

law

C. V-I characteristic, starting with the smallest value of voltage, becomes ohmic

D. Negative differential conductance region appears on V-I characteristic of the diode

The excess hole concentration within the quasi-neutral n-type region of a silicon p+n 

step junction of area A = 1mm × 1mm maintained at T = 300K is plotted on a linear 

scale below. The hole lifetime τp = 10-6 s. ni = 1010 cm-3.(1) Calculate the applied voltage, VA. 

(2) Calculate the minority-carrier charge stored in this diode, QP. 

(3) Calculate the diode current, I.

If the slope of the (1/Cdep)2 vs. VA characteristic of a Si PN step junction is 2 × 1023 

F-2V-1, the intercept is 0.84 V, and A is 104 μm2, find the lighter and heavier doping 

concentrations Nl and Nh. 

Compare Ge diodes to similarly structured and doped Si diodes for the following 

(give reasons): 

(1) Reverse saturation current 

(2) Avalanche breakdown voltage

A tank initially contains 50 gal of fresh water. at t=0 brine solution containing 2 lb of salt per gallon is poured into the tank at the rate of 12 gal/minute. while the well-stirred mixtures leaves the tank at the rate of 8 gal/minutes. what is the amount of salt at the end of the 5 minutes?

A piston cylinder device containing air undergoes a series of two processes. The first process is constant volume process with the pressure decreased from 300 kPaa to 60 kPaa. The second process is compression in accordance with pV1.3 =C. Determine the work done. 

1- The equation for a distance, s(m), travelled in time t(s) by an object starting with an initial velocity u(ms-1) and uniform acceleration a(ms-2) is: 𝑠=𝑢𝑡+12𝑎𝑡2 𝑒𝑞(1) The tasks are to: a) Plot a graph of distance (s) vs time (t) for the first 10s of motion if 𝑢=10𝑚𝑠−1 and 𝑎=5𝑚𝑠−2. b) Find the gradient of the graph at 𝑡=2𝑠 and 𝑡=6𝑠. c) Differentiate the equation to find the functions for i) Velocity (𝑣=𝑑𝑠𝑑𝑡) ii) Acceleration (𝑎=𝑑𝑣𝑑𝑡=𝑑2𝑠𝑑𝑡2)

Draw the logic diagram of a 2-input CMOS NAND & OR gate and explain its working in

brief.