Ch 10. BJT Fundamentalselearning.kocw.net/KOCW/document/2015/korea_sejong/... · 2016-09-09 ·...
Transcript of Ch 10. BJT Fundamentalselearning.kocw.net/KOCW/document/2015/korea_sejong/... · 2016-09-09 ·...
KOREA UNIVERSITY
Photonics Laboratory
Ch 10. BJT Fundamentals
(a) It will be from the one-junction/two-terminal diode to the two-junction/three-terminal
transistor ( the bipolar junction transistor; BJT)
(b) The BJT is a semiconductor device containing three adjoining, alternatively doped regions,
with the middle region being very narrow-compared to the minority carrier diffusion length in the
region.
1
KOREA UNIVERSITY
Photonics Laboratory 2
① Transistor–transistor logic (TTL) is a class of digital circuits built from bipolar
junction transistors (BJT) and resistors.
② It is called transistor–transistor logic because both the logic gating function (e.g.,
AND) and the amplifying function are performed by transistors (contrast with RTL
and DTL).
③ TTL is notable for being a widespread integrated circuit (IC) family used in many
applications such as computers, industrial controls, test equipment and
instrumentation, consumer electronics, synthesizers, etc.
④ After their introduction in integrated circuit form in 1963 by Sylvania, TTL
integrated circuits were manufactured by several semiconductor companies, with
the 7400 series (also called 74xx) by Texas Instruments becoming particularly
popular.
⑤ TTL became the foundation of computers and other digital electronics. Even after
much larger scale integrated circuits made multiple-circuit-board processors
obsolete, TTL devices still found extensive use as the "glue" logic interfacing more
densely integrated components.
(1) Application 1: TTL
KOREA UNIVERSITY
Photonics Laboratory
Two-input TTL NAND gate with a simple output stage (simplified).
3
KOREA UNIVERSITY
Photonics Laboratory 4
KOREA UNIVERSITY
Photonics Laboratory 5
KOREA UNIVERSITY
Photonics Laboratory
① Complementary metal–oxide–semiconductor (CMOS) is a technology for
constructing integrated circuits.
② CMOS technology is used in microprocessors, microcontrollers, static RAM, and
other digital logic circuits.
③ CMOS technology is also used for several analog circuits such as image sensors
(CMOS sensor), data converters, and highly integrated transceivers for many types of
communication. In 1963, while working for Fairchild Semiconductor, Frank Wanlass
patented CMOS (US patent 3,356,858).
④ Two important characteristics of CMOS devices are high noise immunity and low
static power consumption.
⑤ CMOS devices do not produce as much waste heat as other forms of logic, for
example transistor–transistor logic (TTL) or NMOS logic, which normally have some
standing current even when not changing state.
⑥ CMOS also allows a high density of logic functions on a chip. It was primarily for
this reason that CMOS became the most used technology to be implemented in VLSI
chips.
6
(2) Application 2: CMOS
KOREA UNIVERSITY
Photonics Laboratory
CMOS inverter (NOT logic gate)
7
KOREA UNIVERSITY
Photonics Laboratory 8
(3) BJT circuit
KOREA UNIVERSITY
Photonics Laboratory 9
KOREA UNIVERSITY
Photonics Laboratory
. where
0
(-). base and )(emitter ebetween th drop voltagedc theis V example,For EB
ECCE
CEBCEB
CBECEB
CBE
VV
VVV
VVV
III
(4) Biasing modes (pnp)
Biasing mode VEB(E-B junction) VCB(C-B junction)
saturation forward forward
active forward reverse
inverted reverse forward
cutoff reverse reverse
10
http://www.electronics-tutorials.ws/transistor/tran_4.html
http://www.electronics-tutorials.ws/amplifier/amp_2.html
KOREA UNIVERSITY
Photonics Laboratory 11
KOREA UNIVERSITY
Photonics Laboratory 12
(5) BJT structure
KOREA UNIVERSITY
Photonics Laboratory 13
(6) BJT properties
KOREA UNIVERSITY
Photonics Laboratory
reverse B-C forward, B-E :
doping.collector doping basedopingemitter mode. activeunder r transistopnp a (b)
m.equilibriuunder stor npn transi a (a) 10.1)Ex
widthbase alquasineutr the:
W
xxwW nCBnEBB
14
KOREA UNIVERSITY
Photonics Laboratory
(7) Introductory operational considerations:
Let us consider a pnp transistor under active mode biasing.
a. The primary carrier activity in the vicinity of the forward-biased E-B junction is majority
carrier injection across the junction into the opposite-side quasineutral regions.
b. Naturally, the p+-n nature of the junction leads to many more holes being injected from the
emitter into the base than electrons being injected from the base into the emitter.
c. The key to the transistor action is what subsequently happens to the carriers that are injected
into the base.
d. If the quasineutral base width were much larger than a minority carrier diffusion length, the
injected holes would simply recombine in the n-type base and there would be no interaction
between the two junctions.
15
KOREA UNIVERSITY
Photonics Laboratory
e. However, the BJT is a structure where the base is narrow compared to a minority
carrier diffusion length.
f. Thus, the vast majority of injected holes diffuse completely through the quasineutral
base and enter the C-B depletion region.
g. The accelerating electric field in the C-B depletion region then rapidly sweeps the
carriers into the collection.
h. When active mode biased, the emitter functions as a source of carriers, emitting
carriers into the base.
i. Conversely, the collector of the reverse-biased C-B junction acts like a sink,
collecting the emitted carriers after they pass through the base region.
16
KOREA UNIVERSITY
Photonics Laboratory 17
KOREA UNIVERSITY
Photonics Laboratory 18
KOREA UNIVERSITY
Photonics Laboratory
CnBEnBBBB
CEB
CE
CpCEpE
EpEn
En
CnCpCEnEpE
EpCp
IIIIIII
III
II
IIII
II
I
IIIIII
II
Since
2321
CEB
CpCn
CnEn
Cn
biasing. mode activeunder I and I tocompared small very is I
And
,(2) and (1)
(2) II
current, bias-reverse aFor
.components hole respective the tocompared small are I and IBoth *
region.depletion B-C theintor that wandecollector in the electronscarrier minority thefrom arises I *
(1)
And emitter. theinto base thefrominjection electron with associatedcurrent theis where
,
base, in theion recombinatby lost are holes injected theof few very
19
KOREA UNIVERSITY
Photonics Laboratory
(8) Performance parameters
CnCBTdc
CnETCnCpC
ETEpTCp
CBEdcC
Ep
Cp
T
EnEp
Ep
E
Ep
II
IIIII
III
III
I
I
II
I
I
I
a
0
ECB0
dc
0
BC
,(10.10) and (10.8)
(10.10)
)6.10()7.10(
0.I whereflowsat current thcollector the:I
gain.current d.c. basecommon the:
(10.8)
0)(-V mode active At the
gaincurrent d.c. baseCommon (c)
BJT. pnpfor
factor transportBase (b)
BJT. pnpfor
efficiencyemitter The )(
20
KOREA UNIVERSITY
Photonics Laboratory
1 1, ,II
(10.18)
1
(10.17) 1
,(10.16) 1
(10.15) and (10.13) From
(10.15) 11
)1(
)()8.10(
0.I whereflowsat current thcollector the:I
gaincurrent dcemitter common the:
(10.13)
gaincurrent d.c.emitter Common (d)
dcdcBC
0
0
00
0
0
00
BCE0
dc
0
*
I
I
III
II
III
III
IIIIII
III
III
B
Cdc
dc
CBBdcC
dc
CBCE
dc
dcdc
dc
CBB
dc
dcC
CBBdcCdc
CBBCdcCBEdcC
BCE
CEBdcC
21