EEET 201: ELECTRONIC CIRCUITS

PHYS 162: Solid State Devices
(Chapter 1) Introduction to Semiconductors
HW 1 QUESTIONS
DUE DATE: SATURDAY, 1 OCTOBER 2011
Conduction in Semiconductors
1.1 What happens when heat is added to silicon?
1.2 Name the two energy bands where current is produced in silicon.
N-Type and P-Type Semiconductors
1.3 Describe the process of doping and explain how it alters the atomic structure if
silicon.
The Diode
1.4 How is the electric field in the pn junction created?
1.5 Because of its barrier, can a diode be used as a voltage source? Explain.
Biasing a Diode
1.6 Explain why a series resistance is necessary when a diode is forward biased.
Diode Models
1.7 Determine whether each diode in Figure 1.1 is forward-biased or reversed-biased.
1.8 Determine the voltage across each diode in Figure 1.1, assuming the practical model.
1.9 Determine the voltage across each diode in Figure 1.1, assuming the ideal model.
1.10 Determine the voltage across each diode in Figure 1.1, using the complete diode
model with r’ d = 7Ω and r’ R = 100MΩ.
Figure 1.1
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SOLUTION
Conduction in Semiconductors
1.1
1.2
N-Type and P-Type Semiconductors
1.3
The Diode
1.4
1.5
Biasing a Diode
1.6
Diode Models
1.7
1.8
1.9
1.10
Ignoring r′ R
(a) V R ≈ 5V − 8V = −3V
(b)
100V − 0.7V
I F =
560Ω + 7Ω = 175.1mA
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(c)
(d)
V F = I F r ′ d + V B = 175.1mA 7Ω + 0.7V = 1.9V
I tot = 30V
R tot
R tot = 1KΩ + 1.5KΩ + 4.7KΩ = 2.5KΩ + 2.35KΩ = 4.85KΩ
2
I tot =
30V
4.85KΩ = 6.19mA
I F = 6.19mA = 3.1mA
2
V F = I F r ′ d + V B = 3.1mA 7Ω + 0.7V = 0.722V
I F =
20V − 0.7V
10KΩ + 7Ω = 1.93mA
V F = I F r ′ d + V B = 1.93mA 7Ω + 0.7V = 0.71V
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