Transcript Chapter 17 - Transistors and Applications

Fundamental
Electronics—BJT,
CMOS
Reference: Thomas L. Floyd, Electronics Fundamentals: Circuits,
Devices, and Applications, Pearson Education Inc
Reference Books
1
2
3
4
Electronics Fundamentals:
Circuits, Devices, and
Applications
Electronic circuit analysis and
Design
Thomas L.
Floyd
Donald A ,
Neaman
Pearson
Education
Inc.
Irwin
Microelectronics:DIGITAL AND
ANALOG CIRCUITS AND
SYSTEMS
Jacob Millman,
Arvin Grabel
McGrawHill
Microelectronic Circuits
Sedra & Smith
Oxford
Universit
y Press
Objectives
• The History of VLSI
• Describe the basic structure and operation of
bipolar junction transistors (BJT)
• Describe the basic structure and operation of
MOSFETs
• Describe the basic structure and operation of
CMOS
The History of VLSI
• IC(Integrated Circuits) History Evolution
– vacuum tube,
– single transistor,
– IC (Integrated Circuits)
• SSI, MSI, LSI, VLSI, SoC
The History of VLSI
• 1926—Lilienfeld proposed FET
• 1947—Brattin, Bardin, Schockley
proposed BJT from Bell Lab.
• 1957—TI Kilby proposed the first IC
• 1960– Hoerni invent the planar process
• 70’s—IC composed mainly by pMOS
and BJT
The History of VLSI
• 80’s—IC composed mainly by nMOS
and BJT
• 90’s—IC composed mainly by CMOS
and BiCMOS
• 1995—NEC, AT&T, Phillips proposed
SOC
The evolution of IC technique
1947
1950
1961
Tran Singl SSI
sistor e
comp
onent
Logic
Gate
count
Production
----
----
10
----
電晶體
二極體
平面元
件
邏輯閘
暫存器
1966
1971
1980
1985
1990
MSI
LSI
VLSI ULSI GSI
100
~
1000
1000
~
20000
20000
~
500,00
0
>
500,00
0
>
10,000
,000
計數器
多工器
加法器
8bit微
處理器
ROM
RAM
16/32b
its微處
理器
即時影
像處理
器
SOC
Moore’s Law plot
The transistor count in an IC would double every 18
momths
Main Families in Digital Logic
1. TTL(implemented by BJT)—big area,
high consumption, high speed
2. MOS — small area, low consumption,
low speed
3. BiCMOS — speed near TTL, area
near MOS, hard manufacture
Architecture of BJTs
• The bipolar junction transistor (BJT) is
constructed with three doped
semiconductor regions separated by two
pn junctions
• Regions are called emitter, base and
collector
Architecture of BJTs
• There are two types of BJTs, the npn and pnp
• The two junctions are termed the base-emitter
junction and the base-collector junction
• The term bipolar refers to the use of both holes
and electrons as charge carriers in the
transistor structure
• In order for the transistor to operate properly,
the two junctions must have the correct dc bias
voltages
– the base-emitter (BE) junction is forward
biased(>=0.7V for Si, >=0.3V for Ge)
– the base-collector (BC) junction is reverse
biased
FIGURE Transistor symbols.
Thomas L. Floyd
Electronics Fundamentals, 6e
Electric Circuit Fundamentals, 6e
Copyright ©2004 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Basic circuits of BJT
Operation of BJTs
• BJT will operates in one of following
four region
–
–
–
–
Cutoff region (for digital circuit)
Saturation region (for digital circuit)
Linear (active) region (to be an amplifier)
Breakdown region (always be a disaster)
Operation of BJTs
DC Analysis of BJTs
• Transistor Currents:
IE = I C + I B
• alpha (DC)
IC = DCIE
• beta (DC)
IC = DCIB
– DC typically has a value between 20 and
200
DC Analysis of BJTs
• DC voltages for the biased
transistor:
• Collector voltage
VC = VCC - ICRC
• Base voltage
VB = VE + VBE
– for silicon transistors, VBE = 0.7 V
– for germanium transistors, VBE = 0.3 V
Q-point
• The base current, IB, is
established by the
base bias
• The point at which the
base current curve
intersects the dc load
line is the quiescent or
Q-point for the circuit
Q-point
DC Analysis of BJTs
• The voltage divider
biasing is widely
used
• Input resistance is:
RIN  DCRE
• The base voltage is
approximately:
VB  VCCR2/(R1+R2)
BJT as an amplifier
• Class A Amplifiers
• Class B Amplifiers
BJT Class A Amplifiers
• In a class A amplifier, the transistor conducts for
the full cycle of the input signal (360°)
– used in low-power applications
• The transistor is operated in the active region,
between saturation and cutoff
– saturation is when both junctions are forward biased
– the transistor is in cutoff when IB = 0
• The load line is drawn on the collector curves
between saturation and cutoff
BJT Class A Amplifiers
BJT Class A Amplifiers
• Three biasing mode for class A
amplifiers
– common-emitter (CE) amplifier
– common-collector (CC) amplifier
– common-base (CB) amplifier
BJT Class A Amplifiers
• A common-emitter (CE) amplifier
– capacitors are used for coupling ac without
disturbing dc levels
BJT Class A Amplifiers
• A common-collector (CC) amplifier
– voltage gain is approximately 1, but current
gain is greater than 1
BJT Class A Amplifiers
• The third configuration is the
common-base (CB)
– the base is the grounded (common)
terminal
– the input signal is applied to the emitter
– output signal is taken off the collector
– output is in-phase with the input
– voltage gain is greater than 1
– current gain is always less than 1
BJT Class B Amplifiers
• When an amplifier is biased such that it operates
in the linear region for 180° of the input cycle and
is in cutoff for 180°, it is a class B amplifier
– A class B amplifier is more efficient than a
class A
• In order to get a linear reproduction of the input
waveform, the class B amplifier is configured in a
push-pull arrangement
– The transistors in a class B amplifier must be
biased above cutoff to eliminate crossover
distortion
BJT Class B Amplifiers
The BJT as a Switch
• When used as an electronic switch, a
transistor normally is operated alternately
in cutoff and saturation
– A transistor is in cutoff when the base-emitter
junction is not forward-biased. VCE is
approximately equal to VCC
– When the base-emitter junction is forwardbiased and there is enough base current to
produce a maximum collector current, the
transistor is saturated
The BJT as a Switch
An example -- NOR
Architecture of MOS FieldEffect Transistors (FETs)
• The metal-oxide semiconductor fieldeffect transistor (MOSFET) : the gate is
insulated from the channel by a silicon
dioxide (SiO2) layer
Architecture of MOS FieldEffect Transistors (FETs)
• Two types of MOSFETs
– depletion type (D-MOSFETs) have a physical
channel between Drain and Source, with no
voltage applied to the Gate
– enhancement type (E-MOSFETs) have no
physical Drain-Source channel
Architecture of MOS FieldEffect Transistors (FETs)
• D-MOSFET
– Channel may be
enhanced or
restricted by gate
voltage
• E-MOSFET
– Channel is created
by gate voltage
• Simplified
symbol
Biasing Circuits
FET Amplifiers
• Voltage gain of a FET is determined by the
transconductance (gm) with units of
Siemens (S)
gm = Id / Vg
• The D-MOSFET may also be zero-biased
• The E-MOSFET requires a voltage-dividerbias
• All FET’s provide extremely high input
resistance
Principle of MOSFET
for E-MOS (n-channel)
(+)
Principle of MOSFET
for E-MOS (n-channel)
VTN ：The threshold voltage
Principle of MOSFET
for E-MOS (n-channel)
Principle of MOSFET
for D-MOS (n-channel)
Principle of MOSFET
for D-MOS (n-channel)
Voltage-current relations
p-cnannel MOS
(pMOS)
•
S
G
+
P+
-
+++++++
D
-
P+
body
n-substrate
B
All the characteristics are similar to NMOS.
An inverter
Voltage transfer
-- see the time delay
Complementary MOS
(CMOS)
Vss
P
output
input
N
N
P
Vdd
P
Vdd
pMOS
N
in
out
p-well
nMOS
n-substrate
Vss