Transistor

Midterm 2, ECE 448- Spring 2022, UIC Name:

Page 1 of 4

Midterm 2, ECE 448 Transistors - Spring 2022 University of Illinois at Chicago

09:30 am to 10:45 am on March 14, 2022

Name: UIN:

1. [40 points] PROBLEM # 1 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.

a. What is the built-in voltage across the junction? Justify your answer

b. Invoking the depletion approximation, make a sketch of the charge density inside the diode versus x.

c. 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).

Midterm 2, ECE 448- Spring 2022, UIC Name:

Page 2 of 4

d. Draw the energy band diagram for the diode under equilibrium conditions. 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.

Midterm 2, ECE 448- Spring 2022, UIC Name:

Page 3 of 4

3. [30 points] PROBLEM # 3

Given a npn BJT where IEn = 100 μA, IEp = 1 μA, ICn = 99 μA, and ICp = 0.1 μA, calculate: a. αT

b. γ

c. IE, IC, IB

d. αdc

e. βdc

f. ICB0 and ICE0

Midterm 2, ECE 448- Spring 2022, UIC Name:

Page 4 of 4

4. [20 points] PROBLEM # 4

a. What is base-width modulation in a bipolar junction device? How can we reduce the effects of base width modulation?

b. What is meant by graded base in a bipolar junction device? State any advantages

or disadvantages it reflects?