UNIVERSITY OF CALIFORNIA, DAVIS
Department of Electrical and Computer Engineering
EEC111
Digital Electronic Circuits
Spring 2026
Homework #1
Due 11:59pm Tuesday April 14th
Submit a scanned copy of your solutions through Canvas
Reading Assignment: Review Chapter 3, Sections 3.1, 3.2, 3.3, 3.4 and 3.5 of the textbook for the
material covered in this homework.
In solving these problems, if temperature is not given you can assume 𝑇 = 300𝐾. You can also
assume the following values for electron and hole mobility and diffusion constants at 𝑇 = 300𝐾:
Silicon: 𝜇𝑛 = 1350
𝑐𝑚2
𝑉.𝑠
, 𝜇𝑝 = 480
Germanium: 𝜇𝑛 = 3800
𝑐𝑚2
𝑉.𝑠
𝑐𝑚2
𝑉.𝑠
, 𝐷𝑛 = 34
, 𝜇𝑝 = 1800
𝑐𝑚2
𝑉.𝑠
𝑐𝑚2
𝑠
, 𝐷𝑝 = 12
, 𝐷𝑛 = 100
𝑐𝑚2
𝑠
𝑐𝑚2
𝑠
, 𝐷𝑝 = 47
𝑐𝑚2
𝑠
1. Problem 3.1
2. Problem 3.5
3. Problem 3.6
4. Problem 3.7
5. Problem 3.9
6. A n-type piece of silicon with a length of 0.1μm and a cross section area of 0.05μm×0.05μm sustains a
voltage difference of 1V. (a) If the doping level is 1017 𝑐𝑚−3, calculate the total current flowing through
the device at 𝑇 = 300𝐾. (b) Repeat (a) for 𝑇 = 400𝐾 assuming for simplicity that mobility does not
change with temperature.
7. The following figure shows a p-type bar of silicon
that is subjected to electron injection from the left and
hole injection from the right. Determine the total
current flowing through the device if the cross section
area is equal to 1μm×1μm.
8. Consider a bar of silicon in which a hole concentration profile described by 𝑝(𝑥) = 𝑝0 𝑒 −𝑥/𝐿𝑝 is
established. Find the hole-current density at 𝑥 = 0. Let 𝑝0 = 1016 /𝑐𝑚 3 and 𝐿𝑝 = 1𝜇𝑚. If the crosssectional area of the bar is 100 𝜇𝑚2 , find the current 𝐼𝑝 .
9. A p-n junction employs 𝑁𝐷 = 5 × 1017 𝑐𝑚 −3 and 𝑁𝐴 = 4 × 1016 𝑐𝑚−3. (a) Determine the majority and
minority carrier concentrations on both sides. (b) Calculate the built-in potential at 𝑇 = 250𝐾, 300𝐾, and
350𝐾. Explain the trend.