bipolar junction transistors (1) dr. wojciech jadwisienczak ee314
TRANSCRIPT
![Page 1: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/1.jpg)
Bipolar JunctionBipolar Junction Transistors (1) Transistors (1)
Dr. Wojciech Jadwisienczak EE314
![Page 2: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/2.jpg)
Introduction Your goal is to explain the transistor. It is assumed that EE314 students to which this presentation is aimed, have not a clue to how these little Buggers work and/or how to use them. A real problem with previous explanations: for the sake of "fidelity" authors' include confusing details until the concept, or thread--of how they actually work & how to use them--is lost. The following presentation is comprised of several different explanations. You should read chapter 13 and this presentation several times, because any insight gained from one will help in understanding another.
![Page 3: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/3.jpg)
Chapter 13: Bipolar Junction Transistors
pp. 584-624
1.History of BJT2.First BJT3.Basic symbols and features 4.A little bit of physics…5.Currents in BJT’6.Basic configurations7.Characteristics
![Page 4: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/4.jpg)
The transistor was probably the most important invention of the 20th Century, and the story behind the invention is one of clashing egos and top secret research.
First - BJTs
Reference:Bell Labs MuseumB. G. Streetman & S. Banerjee ‘Solid State Electronic Devices’, Prentice Hall 1999.
![Page 5: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/5.jpg)
Picture from previous slide shows the workbench of John Bardeen and Walter Brattain at Bell Laboratories. They were supposed to be doing fundamental research about crystal surfaces. The experimental results hadn't been very good, though, and there's a rumor that their boss, William Shockley, came near to canceling the project. But in 1947, working alone, they switched to using tremendously pure materials. It dawned on them that they could build the circuit in the picture. It was a working amplifier! John and Walter submitted a patent for the first working point contact transistor. Shockley was furious and took their work and invented the junction transistor and submitted a patent for it 9 days later. The three shared a Nobel Prize. Bardeen and Brattain continued in research (and Bardeen later won another Nobel). Shockley quit to start a semiconductor company in Palo Alto. It folded, but its staff went on to invent the integrated circuit (the "chip") and to found Intel Corporation. By 1960, all important computers used transistors for logic, and ferrite cores for memory.
Interesting story…
![Page 6: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/6.jpg)
Point-Contact Transistor – first transistor ever made
![Page 7: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/7.jpg)
![Page 8: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/8.jpg)
Qualitative basic operation of point-contact transistor
Problems with first transistor…
![Page 9: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/9.jpg)
First Bipolar Junction TransistorsW. Shockley invented the p-n junction transistorThe physically relevant region is moved to the bulk of the material
![Page 10: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/10.jpg)
Understanding of BJT
force – voltage/currentwater flow – current - amplification
![Page 11: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/11.jpg)
Basic models of BJT
Diode
Diode
Diode
Diode
npn transistor
pnp transistor
![Page 12: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/12.jpg)
Qualitative basic operation of BJTs
![Page 13: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/13.jpg)
Basic models of BJT
![Page 14: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/14.jpg)
BJTs – Basic ConfigurationsFluid Flow AnalogyDifference between FET (field effect transistor) and BJTTechnology of BJTs
pnp BJT npn BJT
![Page 15: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/15.jpg)
BJTs – Practical Aspects
Heat sink
![Page 16: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/16.jpg)
BJTs – Testing
![Page 17: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/17.jpg)
BJTs – Testing
![Page 18: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/18.jpg)
A little bit of physics…
![Page 19: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/19.jpg)
A little bit of physics…
![Page 20: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/20.jpg)
A little bit of physics…
![Page 21: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/21.jpg)
A little bit of physics…
![Page 22: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/22.jpg)
A little bit of physics…
![Page 23: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/23.jpg)
More accurate physical description…
pnp BJT
1. Injected h+ current from E to B2. e- injected across the forward-biased EB junction
(current from B to E)3. e- supplied by the B contact for recombination with h+
(recombination current)4. h+ reaching the reverse-biased C junction5,6.Thermally generated e- & h+ making up the reverse
saturation current of the C junction
iE
-iB
-iC
-VCE
![Page 24: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/24.jpg)
Now, you can try…
npn BJT
![Page 25: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/25.jpg)
BJTs – Basic configurations
![Page 26: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/26.jpg)
npn BJTs – Operation Modes
Forward & reverse polarized pn junctions
Different operation modes:
![Page 27: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/27.jpg)
npn BJTs – Operation Modes
•When there is no IB current almost no IC flows•When IB current flows, IC can flow•The device is then a current controlled current device
Operational modes can be defined based on VBE and VBC
![Page 28: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/28.jpg)
BJT-Basic operation
npn BJTpnp BJT
(n+), (p+) – heavy doped regions; Doping in E>B>C
![Page 29: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/29.jpg)
Operation mode: vBE is forward & vBC is reverse
The Shockley equation
1exp
T
BEESE V
vIi
IES–saturation I (10-12-10-16A); VT=kT/q -thermal V (26meV) D – diffusion coefficient [cm2/s] – carrier mobility [cm2/Vs]The Kirchhoff’s laws
BCE iii
EiIt is true regardless of the bias conditions of the junction
Useful parameter
B
C
i
i
the common-emitter current gainfor ideal BJT is infinite
0 CEBCBE VVV
BJTs – Current & Voltage Relationships
q
kTD
Einstein relation
![Page 30: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/30.jpg)
1exp
T
BEESC V
vIi
E
C
i
iUseful
parameterthe common-base current gainfor typical BJT is ~0.99
The Shockley equationonce more
If we define the scale current
ESS II
T
BESC V
vIi
A little bit of math… search for iB
EB ii 1
1exp1
T
BEESB V
vIi
1B
C
i
i
BC ii Finally…
BJTs – Current & Voltage Relationships
![Page 31: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/31.jpg)
BJTs – Characteristics
SchematicCommon-Emitter
Input
Output
VBC<0 or equivalently VCE>VBE
If VCE<VBE the B-C junction is forward bias and IC decreasesRemember VBE has to be greater than 0.6-07 V
BC ii
Example 13.1
![Page 32: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/32.jpg)
BJTs – Load line analysisCommon-Emitter Amplifier
)()()( tvtiRtvV BEBBinBB Input loop
if iB=0 inBBBE vVv if vBE=0 BinBBE RvVi /)(
smaller vin(t)
![Page 33: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/33.jpg)
BJTs – Load line analysis
CECCCC viRV Output loop
Common-Emitter Amplifier
Example 13.2
![Page 34: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/34.jpg)
Circuit with BJTs
Our approach: Operating point - dc operating pointAnalysis of the signals - the signals to be amplified
Circuit is divided into: model for large-signal dc analysis of BJT circuitbias circuits for BJT amplifiersmall-signal models used to analyze circuits for signals being amplified
Remember !
![Page 35: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/35.jpg)
Large-Signal dc Analysis: Active-Region Model
Important: a current-controlled current source models the dependence of the collector current on the base current
The constrains for IB and VCE must be satisfy to keep BJT in the active-mode
VBE
forward bias
VCB
reverse bias ?
?
![Page 36: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/36.jpg)
Large-Signal dc Analysis: Saturation-Region Model
VBE
forward bias
VCB
forward bias?
?
![Page 37: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/37.jpg)
Large-Signal dc Analysis: Cutoff-Region Model
VCB
reverse bias
VBE
reverse bias
?
?
If small forward-bias voltage of up to about 0.5 V are applied, the currents are often negligible and we use the cutoff-region model.
![Page 38: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/38.jpg)
Large-Signal dc Analysis: characteristics of an npn BJT
![Page 39: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/39.jpg)
Large-Signal dc Analysis
Procedure: (1) select the operation mode of the BJT (2) use selected model for the device to solve the circuit
and determine IC, IB, VBE, and VCE (3) check to see if the solution satisfies the constrains for
the region, if so the analysis is done (4) if not, assume operation in a different region and repeat until a valid solution is found
This procedure is very important in the analysis and design of the bias circuit for BJT amplifier.
The objective of the bias circuit is to place the operating point inthe active region.
Bias point – it is important to select IC, IB, VBE, and VCE
independent of the and operation temperature.
Example 13.4, 13.5, 13.6
![Page 40: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/40.jpg)
Large-Signal dc Analysis: Bias Circuit
From Example 13.6
Remember: that the Q point should be independent of the stability issue) VBB & VCC provide this stability, however this impractical solutionOther approach is necessary to solve this problem-resistor network
VBB acts as a short circuit for ac signals
![Page 41: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/41.jpg)
Large-Signal dc Analysis: Four-Resistor Bias Circuit
1
2
3
4
Thevenin equivalent
21 RRRB 212 / RRRVV CCB
Equivalent circuit for active-region model
Solution of the bias problem:
Input Outpu
t
EEBEBBB IRVIRV
BE II 1 VVBE 7.0
EB
BEBB RR
VVI
1
EECCCCCE IRIRVV
![Page 42: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/42.jpg)
npn
BJTs – Practical Aspects
![Page 43: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/43.jpg)
R
VI
![Page 44: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/44.jpg)
![Page 45: Bipolar Junction Transistors (1) Dr. Wojciech Jadwisienczak EE314](https://reader033.vdocuments.mx/reader033/viewer/2022051216/56649cdd5503460f949a80ca/html5/thumbnails/45.jpg)
http://www.4p8.com/eric.brasseur/vtranen.html