2/11/2019 1 Lecture 0 Course Overview EE206 Electronics I • Course description: Theory, characteristics and operation of diodes, bipolar junction transistors and MOSFET transistors. • When: Tue Thu 10:30-12:20 (Lectures) • Textbook: Fundamentals of Microelectronics; 2nd ed. Razavi •Recommended references supporting the course B. Streetman, S. Banerjee (1999).Solid State Electronic Devices, Prentice Hall, ISBN 0130255386. Robert L. Boylestad, Louis Nashelsky, (2013) Electronic devices and circuit theory, 11th edition, Pearson Education Neamen D.A., (2007), Microelectronics Circuit Analysis and Design, McGraw Hill.
25
Embed
ese206 SP 2019 lecture 1 intro · Develop an understanding of the Bipolar Junction Transistor (BJT) and its operation. Identify and describe the different BJT configurations, DC biasing,
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
2/11/2019
1
Lecture 0
Course Overview
EE206 Electronics I
• Course description: Theory, characteristics and operation of diodes, bipolar junction transistors and MOSFET transistors.
• When: Tue Thu 10:30-12:20 (Lectures)
• Textbook: Fundamentals of Microelectronics; 2nd ed. Razavi•Recommended references supporting the course
B. Streetman, S. Banerjee (1999).Solid State Electronic Devices, PrenticeHall, ISBN 0130255386.Robert L. Boylestad, Louis Nashelsky, (2013) Electronic devices and circuittheory, 11th edition, Pearson EducationNeamen D.A., (2007), Microelectronics Circuit Analysis and Design,McGraw Hill.
2/11/2019
2
Course Assessment
Lecture 01 3
Assessment Type Percentage Time
Midterm 20% Week 8
Lab 20%Every 2 Weeks
Assignment/Quiz 20% Every Week
Final Exam 20% Week 16
Project 20% Week 17
Total mark 100%
Weeks Topics
1 Introduction, Basics of semiconductor physics
2 Intrinsic & Extrinsic semiconductors
3 PN-junction4 PN-diodes and their applications5 Bipolar junction transistor (BJT) I6 Bipolar junction transistor (BJT) II7 Bipolar junction transistor (BJT) III8 Midterm9 FET transistor I
10 FET transistor II11 FET transistor III12 CMOS Technology13 CMOS Amplifiers14 OPAMP as a black box
Identify and describe operation of semiconductor devices throughunderstanding of the semiconductor physics.
Develop an understanding of the PN junction diode and its behavior. Develop an ability to analyze diode circuits and examine additional
applications of the diode. Develop an understanding of the Bipolar Junction Transistor (BJT) and
its operation. Identify and describe the different BJT configurations, DC biasing, and
AC analysis. Develop an understanding of the Field Effect Transistor (FET) and its
operation. Identify and describe the different FET configurations, DC biasing, and
AC analysis. Develop an understanding of the CMOS circuit and its operation. Develop an understanding of the OPAMP circuits.
2/11/2019
4
EXPECTED OUTCOMEUpon successful completion of the course, students will be ableto: Acquire some understanding in the fundamental electric and
electronics principles. Describe the operation and i-v characteristics of diodes and
transistors. Solve basic problems in electronic circuits. Implement different applications using basic electronic
devices (diodes and transistors). Read and understand the datasheets of diodes and transistors
to use the suitable parts in design. Design and analyze electronic circuits use computer
packages (simulators). Acquire better skills in performing the laboratory experiments. Work as a team in laboratory sessions.
2/11/2019 Lecture 01 7
Electronic Circuit Design Steps
• Theory: Semiconductor Physics, Circuit Theory.
• Analysis: DC and AC (small and large signal)modeling
• Simulation: CAD Tools, Spice and derivatives• Implementation: Breadboard and PCB
Testing.
2/11/2019 Lecture 01 8
2/11/2019
5
Simulators
2/11/2019 Lecture 01 9
Multisim (National Instruments)
TINA
LTSPICE
Altium, Proteus, Cadence (Advanced and
licensed)
https://www.eetimes.com/document.asp?doc_id=13
26778#
10
• 1.1 Electronics versus Microelectronics
• 1.2 Example of Electronic System: Cellular Telephone
• 1.3 Analog versus Digital
Chapter 1 Why Microelectronics?
2/11/2019
6
Why Electronics?
CH1 Why Microelectronics? 12
Cellular Technology
• An important example of microelectronics.• Microelectronics exist in black boxes that process the
received and transmitted voice signals.
2/11/2019
7
CH1 Why Microelectronics? 13
Frequency Up-conversion
• Voice is “up-converted” by multiplying two sinusoids.• When multiplying two sinusoids in time domain, their
spectra are convolved in frequency domain.
CH1 Why Microelectronics? 14
Transmitter
• Two frequencies are multiplied and radiated by an antenna in (a).
• A power amplifier is added in (b) to boost the signal.
2/11/2019
8
CH1 Why Microelectronics? 15
Receiver
• High frequency is translated to DC by multiplying by fC.• A low-noise amplifier is needed for signal boosting without
excessive noise.
CH1 Why Microelectronics? 16
Digital or Analog?
• X1(t) is operating at 100Mb/s and X2(t) is operating at 1Gb/s.
• A digital signal operating at very high frequency is very “analog”.
2/11/2019
9
17
Chapter 2 Basic Physics of Semiconductors
• 2.1 Semiconductor materials and their properties
• 2.2 PN-junction diodes
• 2.3 Reverse Breakdown
CH2 Basic Physics of Semiconductors 18
Semiconductor Physics
• Semiconductor devices serve as heart of microelectronics.
• PN junction is the most fundamental semiconductor device.
2/11/2019
10
CH2 Basic Physics of Semiconductors 19
Charge Carriers in Semiconductor
• To understand PN junction’s IV characteristics, it is important to understand charge carriers’ behavior in solids, how to modify carrier densities, and different mechanisms of charge flow.
CH2 Basic Physics of Semiconductors 20
Periodic Table
• This abridged table contains elements with three to five valence electrons, with Si being the most important.
2/11/2019
11
Valence Electrons• Valence electrons: electrons in the outermost shell.
– Electrons that are in orbits farther from the nucleus have higher energy and are less tightly bound to the atom than those close to the nucleus.
– Electrons with the highest energy exist in the outermost shell of an atom and are relatively loosely bound to the atom.
Silicon Atom
Silicon has four valence electrons.
2/11/2019
12
Sharing of Electrons in Silicon
A silicon atom with its four valence electrons shares an electron with each of its four neighbors. This effectively creates eight shares valence electrons for each atom and produces a state of chemical stability.The sharing of valence electrons produce the covalent bonds that hold the atoms together; each valence electron is attracted equally by the two adjacent atoms which share it.
CH2 Basic Physics of Semiconductors 24
Silicon
• Si has four valence electrons. Therefore, it can form covalent bonds with four of its neighbors.
• When temperature goes up, electrons in the covalent bond can become free.
2/11/2019
13
Sharing of Electrons in Silicon
At T=0K
Electrons gain thermal energy and break away from the bonds. They begin to act as “free charge carriers”—free electron.
An electron leave behind a void because the bond is now incomplete. A void is called a hole. A hole can absorb an free electron if one becomes available.
2/11/2019
14
One electron has traveled from right to left.One hole has traveled from left to right.
Bandgap EnergyQ:Does any thermal energy create free electrons (and holes) in silicon?
A: No. A minimum energy—called the “bandgap energy” is required to dislodge an electron from a covalent bond. For silicon, the bandgap energy is 1.12 eV. Note: eV represents the energy necessary to move one electron across a potential difference of 1V. 1 eV =1.6 x 10-19 J
Insulators display a higher Eg . (e.g. 2.5 eV for diamond)Semiconductors usually have a moderate Eg between 1 eV and 1.5 eV.
2/11/2019
15
Electron DensityQ: How many free electrons are created at a given temperature?
15 3 2 35 2 10 exp electrons cm2
gi
En T
kT
where k=1.38 x 10-23 J/K is called the Boltzmann constant.
As expected, materials having a larger bandgap(Eg)exhibit a smaller ni . Also, as T approaches zero, niapproaches zero.
Making sense of electron density
Determine the electron density in silicon at T=300K.Use the electron density formula with Eg=1.12 eV, ni @ 300 T is 1.08 x 1010
Electrons per cm3.
Silicon has 5 x 1022 atoms per cm3.
What this means is that there is one electron for 5 x 1012 atoms at room temperature.
2/11/2019
16
Intrinsic Semiconductor
The pure silicon has few electrons incomparison to the numbers of atoms.Therefore, it is somewhat resistive.
In an intrinsic semiconductors, the electrondensity(n or ni) is equal to the hole density (p).(each electron is created by leaving behind ahole.)So
np=ni2
2/11/2019
17
CH2 Basic Physics of Semiconductors 33
Free Electron Density at a Given Temperature
• Eg, or bandgap energy determines how much effort is needed to break off an electron from its covalent bond.
• There exists an exponential relationship between the free-electron density and bandgap energy.
3150
3100
32/315
/1054.1)600(
/1008.1)300(
/2
exp102.5
cmelectronsKTn
cmelectronsKTn
cmelectronskT
ETn
i
i
gi
CH2 Basic Physics of Semiconductors 34
Doping (N type)
• Pure Si can be doped with other elements to change its electrical properties.
• For example, if Si is doped with P (phosphorous), then it has more electrons, or becomes type N (electron).
2/11/2019
18
Phosphorus has 5 valence electrons. The 5th electron is “unattached”. This electron is free to move and serves as a charge carrier.
Doping
The controlled addition of an impurity such as phosphorus to an intrinsic (pure) semiconductor is called “doping”. And phosphorus itself is a dopant.
Providing many more free electrons than in the intrinsic state, the doped silicon crystal is now called “extrinsic,” more specifically, an “ n-type” semiconductor to emphasize the abundance of free electrons.
2/11/2019
19
Hole density in an n-type semiconductor
Many of the new electrons donated by the dopant “recombine” with the holes that were created in the intrinsic material. As a consequence, in an n-type semiconductor. The hole density will drop below its intrinsic level.
np=ni2
In an n-type semiconductor, Electrons are the majority carriers.Holes are the minority carriers.If a voltage is applied across an n-type materials, the current consists predominantly of electrons.
CH2 Basic Physics of Semiconductors 38
Doping (P type)
• If Si is doped with B (boron), then it has more holes, or becomes type P.
2/11/2019
20
if we can dope silicon with an atom that provides an insufficient number of electrons, then we may obtain many incomplete covalent bonds.A boron has only 3 valence electrons and can form only 3 covalent bonds. Therefore, it contains a hole and is ready to absorb a free electron.
Summary
MajorityCarriers Dn N 2
MinorityCarriers i
D
np
N
MajorityCarriers Ap N 2
MinorityCarriers i
A
nn
N
In n-type material,
In p-type material,
2/11/2019
21
CH2 Basic Physics of Semiconductors 41
Summary of Charge Carriers
CH2 Basic Physics of Semiconductors 42
First Charge Transportation Mechanism: Drift
• The process in which charge particles move because of an electric field is called drift.
• Charge particles will move at a velocity that is proportional to the electric field.
Ev
Ev
ne
ph
2/11/2019
22
CH2 Basic Physics of Semiconductors 43
Current Flow: General Case
• Electric current is calculated as the amount of charge in v meters that passes thru a cross-section if the charge travel with a velocity of v m/s.
qnhWvI
CH2 Basic Physics of Semiconductors 44
Epnq
qpEqnEJ
qnEJ
pn
pntot
nn
)(
Current Flow: Drift
• Since velocity is equal to E, drift characteristic is obtained by substituting V with E in the general current equation.
• The total current density consists of both electrons and holes.
2/11/2019
23
CH2 Basic Physics of Semiconductors 45
Velocity Saturation
• A topic treated in more advanced courses is velocity saturation.
• In reality, velocity does not increase linearly with electric field. It will eventually saturate to a critical value.
E
v
Ev
bv
bE
sat
sat
0
0
0
0
1
1
CH2 Basic Physics of Semiconductors 46
Second Charge Transportation Mechanism: Diffusion
• Charge particles move from a region of high concentration to a region of low concentration. It is analogous to an every day example of an ink droplet in water.
2/11/2019
24
CH2 Basic Physics of Semiconductors 47
Current Flow: Diffusion
• Diffusion current is proportional to the gradient of charge (dn/dx) along the direction of current flow.
• Its total current density consists of both electrons and holes.
dxdn
qDJ
dxdn
AqDI
nn
n
)(dxdp
Ddxdn
DqJ
dxdp
qDJ
pntot
pp
CH2 Basic Physics of Semiconductors 48
Example: Linear vs. Nonlinear Charge Density Profile
• Linear charge density profile means constant diffusion current, whereas nonlinear charge density profile means varying diffusion current.
LN
qDdxdn
qDJ nnn dd
nn L
xL
NqDdxdn
qDJ
exp
2/11/2019
25
CH2 Basic Physics of Semiconductors 49
Einstein's Relation
• While the underlying physics behind drift and diffusion currents are totally different, Einstein’s relation provides a mysterious link between the two.