1. EE141
Microelectronic Circuits Chapter 10. Semiconductors, Diodes, and Power Supplies
School of Computer Science and Engineering
Pusan National University
Jeong Goo Kim

2. 10-1 Introduction Diode two-terminal electronic device
forward bias; conducts current
reverse bias; refuses to conduct current
“check “ valves or “flapper” valves

3. 10-2 p- and n-Type Semiconductors
Elements surrounding silicon in periodic table
group four elements
covalent bonds
form crystal lattice → poor conductor

4. Dopping n-Type silicon p-Type silicon intrinsic ; pure silicon
10-2 Semiconductors
Dopping
intrinsic ; pure silicon
dopants ; impurities
n-Type silicon
donor
Phosphorus
free electron
p-Type silicon
acceptor
Boron
hole

5. n-type material p-type material Intrinsic material
10-2 Semiconductors
n-type material
free electron concentration, n, in electrons/cm n ≈ ND here ND is the donor atom dopping density in atoms/cm3
ND > NA and n>p
p-type material
free hole concentration, p, in holes/cm p ≈ NA here NA is the acceptor atom dopping density in atoms/cm3
NA > ND and p > n
Intrinsic material
Intrinsic carrier concentration, ni ni = n = p for silicon at 300°K, ni ≈ 1.6×1010 electrons/cm3

6. 10-3 Current Conduction in Semiconductors
Electric current
electron and hole
drift and diffusion current
Drift
Electric field vector
Electron drift velocity
Hole drift velocity for silicon and

7. 10-3 Current Conduction in Semiconductors
Conductivity
Resistivity
Resistance
Example 10.1
Current density
Example 10.2

8. 10-3 Current Conduction in Semiconductors
Diffusion
Movement from a region of high concentration to a region of lower concentration.
Diffusion current density dn/dx is the electron concentration gradient Dn is the diffusion constant for silicon at 300°K and
Example 10.3

9. 10-4 The p-n Junction Diode
depletion region

10. 10-4 The p-n Junction Diode
Potential barrier
Forward and reverse bias Forward bias Reverse bias

11. 10-5 Diode Circuit Models Symbol and physical structure
The Ideal Diode
V-I curve symbol switch model

12. 10.5.2 Diode Equation and Model
10-5 Diode Circuit Models
Diode Equation and Model
Diode equation ID : diode current Io : reverse saturation current q : electronic charge VD : voltage across the diode k: Boltzmann’s constant T: temperature
V-I curve with equation and series resistance

13. 10.5.3 The Piecewise Linear Diode Model
10-5 Diode Circuit Models
The Piecewise Linear Diode Model
Turn-off voltage VF 1 μA as the threshold of conduction, for silicon VF=0.7V
V-I curve for piecewise linear model and symbol
Examples

14. 10-6 Power Supply Circuits
EE141
10-6 Power Supply Circuits
Typical input section of a power supply
Transformer is used to step down the voltage

15. 10-6 Power Supply Circuits
Half-Wave Rectification
Example 10.11
Average output voltage

16. 10-6 Power Supply Circuits
Example Half-Wave Rectifier with PL Diode model

17. 10-6 Power Supply Circuits
EE141
Filter Circuits for Half-Wave Rectification
filter : produce smooth dc from ac input
ripple : small variation in voltage from filter output

18. 10-6 Power Supply Circuits
EE141
Calculation of ripple magnitude
ripple factor, RF

19. 10-6 Power Supply Circuits
EE141
Full-Wave Rectification
dc value of full-wave rectifier
Alternation

20. 10-7 Wave Shaping: Clippers and Clampers
Clipper Circuits
are used to limit the voltage excursions of a signal at a positive value, at a negative value, or both.
Example 10.14

21. 10-7 Wave Shaping: Clippers and Clampers
Clamping Circuit
is circuit that produces an output that appears just as input with one exception-the dc level or average voltage is shifted positively or negatively.

22. 10-8 The Zener or Avalanche Diode
Breakdown
if reverse voltage increase high, a diode conducts a large current in the reverse direction.
the reverse current remains extremely small until the reverse bias voltage reaches breakdown voltage, called avalanche or zener breakdown voltage, Vz.

23. 10-9 Load Lines and Graphical Solutions
current ID
by diode equation
loop equation

24. 10-10 Photo Diode and Light Emitting Diode
10-10 Photo Diode and LED
10-10 Photo Diode and Light Emitting Diode
Photo diode
is used to convert incident radiation to electrical current
Solar cell is a large p-n diode which creates electron-hole pairs in the depletion region from the sun’s radiation.
are also used for light intensity meters.
LED
are p-n junction with Ga-As semiconductor.
release energy in the form of light.

25. Chapter 11. Transistor Fundamentals
Homework
EE141
Homework
Read textbook pp
Solve problems 9, 16, 19, 24, 26, 34, 38, 40, 43, 47, 49, 52
Next Lecture
Chapter 11. Transistor Fundamentals