Midterm 2, ECE 448 Transistors – Spring 2022 – Homework Solution
Midterm 2, ECE 448 Transistors – Spring 2022
University of Illinois at Chicago
09:30 am to 10:45 am on March 14, 2022
Name:Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â UIN:-ECE 448 Transistors
- [40 points] PROBLEM # 1
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Midterm 2, ECE 448 Transistors – Spring 2022 – Homework Solution
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A pn junction has the doping profile sketched below. Throughout the problem assume the carrier concentrations may be neglected (n=0, p=0) in the 0 ≤ x ≤ xi region of the diode.
- What is the built-in voltage across the junction? Justify your answer
- Invoking the depletion approximation, make a sketch of the charge density inside the diode versus x.
- Obtain an analytical solution for the electric field, E(x) at all points inside the depletion regions (-xp ≤ x ≤ xn). Show all steps and also make a sketch of E(x).
- Draw the energy band diagram for the diode under equilibrium Clearly indicate x = 0 and x= xi points on your diagram.
2.     [10 points] PROBLEM # 2
Establish a small-signal equivalent model for the common base configuration. Provide a summary of all the device parameters.
3.     [30 points] PROBLEM # 3
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Given a npn BJT where IEn  = 100 μA, IEp  = 1 μA, ICn  = 99 μA, and ICp  = 0.1 μA, calculate:
- αT
- γ
- IE, IC, IB
- αdc
- βdc
- ICB0 and ICE0
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4.     [20 points] PROBLEM # 4
- What is base-width modulation in a bipolar junction device? How can we reduce the effects of base width modulation?
- What is meant by graded base in a bipolar junction device? State any advantages or disadvantages it reflects?
