中中中中中中中 中中中 Electronics I, Neamen 3th Ed. 1 The Bipolar Junction Transistor (BJT) 中中中 中中中中 中中中中中 [email protected] CO2005: Electronics I
Dec 25, 2015
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 1
The Bipolar Junction Transistor (BJT)
張大中中央大學 通訊工程系
CO2005: Electronics I
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 2
Bipolar Transistor Structures
1910DN
1510DN
1710PN
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 3
Forward-Active Mode in the NPN Transistor
e
Because of the large concentration gradient in the base region, electrons injected from the emitter diffuse across the base into the BC space-charge region, where the E-field sweeps them into the collector region.
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 4
Emitter Current: Exponential function of the BE voltage Collector Current: Ignoring the recombination in the base region (the base width is very
tiny, micrometer), the collect current is proportional to the emitter injection current and is independent of the reverse-biased BC voltage. Hence, the collector current is controlled by the BE voltage.
Base Current: BE forward-biased current Base recombination current
Currents in Emitter, Collector, and Base
1Bi
2Bi
CBCBE
BC
BPED
iiiii
ii
NN
1
1
,,
,
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 5
Common-Emitter Configuration
B
C
i
i
BCBE iiii )1(
EC ii)1(
Common-emitter current gain
The power supply voltage Vcc must be sufficiently large to keep BC junction reverse biased.
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 6
Forward-Active Mode in the PNP Transistor
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 7
Circuit Symbols and Conventions
The arrowhead is always placed on the emitter terminal, and it indicates the direction of the emitter current.
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 8
Common-Emitter Circuits
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 9
For forward-active mode, the BC junction must be reverse biased, which means that Vce must be greater than approximately Vbe(on). There is a finite to the curves.
Current-Voltage Characteristics for CE Voltage
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 10
When the current-voltage characteristic curves are extrapolated to zero current, they meet at a point on the negative voltage axis at Vce=-Va, the early voltage.
The slope of the curves indicates that the output resistance looking into the collector is finite. The resistance is not critical in the dc analysis.
Early Voltage
.
1
constvCE
C
oBE
v
i
r
currentcollector quiescent the:
,
C
C
Ao
I
I
Vr
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 11
Common-Base CharacteristicsFor the curves in which , breakdown begins earlier. The carriers flowing across the junction initiates the breakdown avalanche process at somewhat lower voltages.
Breakdown Voltage
0Ei
Emitter is open.
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 12
DC Analysis of Common-Emitter Circuit for NPN
BCB
BEBBB II
R
VVI
and
)on(
CCCCCECECCCC RIVVVRIV
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 13
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 14
DC Analysis of Common-Emitter Circuit for PNP
BCB
EBBBB II
R
VVI
and
)on(
CCCCEC RIVV
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 15
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 16
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 17
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 18
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 19
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 20
Cutoff and Saturation
Cutoff:
Saturation:
Transistor Circuit Application: Switch
CCO
CBBEI
Vv
iionVv
0 ),(
)(
/ ,
satVv
RRVv
CEO
CBCCI
B
BEIB R
onVvi
)(
C
CECCCc R
satVVsatIi
)()(
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 21
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 22
Bipolar Inverter
Multiple-input NOR gate
Transistor Circuit Application: Digital Logic
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 23
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 24
Single Base Resistor Biasing
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 25
Voltage Divider Biasing
21 // RRRTH
CCTH VRR
RV
21
2
EBQBETHBQTH RIonVRIV )1()(
ETH
BETHBQ RR
onVVI
)1(
)(
BQCQ II
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 26
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 27
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 28
Bias Stability
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 29
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 30
Positive and Negative Voltage Biasing
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 31
For integrated circuits, we would like to eliminate as many resistors as possible since, in general, they require a larger surface than transistors.
Integrated Circuit Biasing
VonVRI BE )(0 11
11
))((
R
VonVI BE
22
2
212111
)2
1(2
2
CC
C
BCBBC
II
I
IIIIII
112 )2
1( IIIC
Reference current
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 32
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 33
Multistage Circuits
1.12I5
V5B2
C1
2101
0.7V5I C1
B2
2.39mAI0.0237mA,I E2B2
0.22V2.3925 V0.48V,V E2C1
1.445V2.371.55VC2
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 34
中央大學通訊系 張大中 Electronics I, Neamen 3th Ed. 35