n pn pnp transistor lesson 01 a
Post on 08-Aug-2018
219 Views
Preview:
TRANSCRIPT
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
1/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 1
Transistor and their
Characteristics
Lesson-1 Junction Transistor
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
2/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 2
1.1. Junction TransistorJunction Transistor
DefinitionDefinition
The transferred-resistance or transistor
is a multi-junction device that is capableof
Current gain
Voltage gain Signal-power gain
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
3/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 3
Bipolar junction transistorBipolar junction transistor
Invented in 1948 by Bardeen, Brattain andShockley
Contains three adjoining, alternately doped
semiconductor regions: Emitter (E), Base (B), andCollector (C)
The middle region, base, is very thin compared
to the diffusion length of minority carriers
Two kinds: npn and pnp
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
4/29
2008Junction Transistor Unit 4 Lesson 1-
" , Raj Kamal,4
Bipolar junction transistor BJT
Definition
The Bipolar junction transistor is an active
device that works as a voltage-controlledcurrent source and whose basic action is
control of current at one terminal by
controlling voltage applied at other two
terminals.
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
5/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 5
Bipolar Junction Transistor Representation
NPN PNP
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
6/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 6
2.2. Transistor CurrentTransistor Current
ComponentsComponents
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
7/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 7
BJT circuit Current ComponentsBJT circuit Current Components
As shown, the currents are positive quantities when the
transistor is operated in forward active mode.
IE =IB +IC and VEB + VBC + VCE = 0 VCE = VEC
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
8/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 8
Meaning of Forward biasingMeaning of Forward biasing
When the p side is applied +ve and n side
negative in a junction and applied voltage is
grater than a threshold 0.65 V for Silicon
(Si)
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
9/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 9
Meaning of Reverse biasingMeaning of Reverse biasing
When the p side is applied -ve and n side
+ve in a junction and applied voltage is
between 0 to a breakdown voltage
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
10/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 10
3.3. Transistor as AmplifierTransistor as Amplifier
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
11/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 11
BJT CommonBJT Common
BaseBase
configurationconfiguration
BJT CommonBJT Common
EmitterEmitter
configurationconfiguration
BJT CommonBJT Common
CollectorCollector
configurationconfiguration
PNPPNP PNP
IBIE IC
Three configurations
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
12/29
2008Junction Transistor Unit 4 Lesson 1-
" , Raj Kamal,
12
Six Problems
Draw circuits of CB, CE, CC
configurations for npn and pnp transistors Show current directions
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
13/29
2008Junction Transistor Unit 4 Lesson 1-
" , Raj Kamal,
13
npn transistor ina simple circuit, known as
common-emitteramplifier
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
14/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 14
Characteristics ofCharacteristics of Transistor Amplifier in threeTransistor Amplifier in three
regions of operationsregions of operations
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
15/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 15
Input or driving PointInput or driving Point
Characteristics of CommonCharacteristics of Common
Base transistor AmplifierBase transistor Amplifier
Input or driving Point
Characteristics of Common
Emitter transistorAmplifier
Active region
Saturation region Saturation region
Active region
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
16/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 16
Output CollectorOutput Collector
Characteristics of CommonCharacteristics of Common
Base transistor AmplifierBase transistor Amplifier
Output CollectorOutput Collector
Characteristics of CommonCharacteristics of Common
Emitter transistorEmitter transistor
AmplifierAmplifier
Saturation region Cut-off region Cut-off regionSaturation region
Active region Active region
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
17/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 17
First Approximation RelationshipFirst Approximation Relationship
betweenbetween IICC andand IIEE IC IE
BJT CommonBJT Common
BaseBase
configurationconfiguration
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
18/29
2008Junction Transistor Unit 4 Lesson 1-
" , Raj Kamal,
18
The collector current is being controlled by the B-E voltage, orthe current in the one part of the device is being controlled bythe voltage in another part - transistor action
Since the B-E junction is forward biased, holes from the baseare injected into the emitter. However, these injected holesdo not contribute to the collector current and are thereforenot part of the transistor action
To design a useful device, we need mathematical expressionsfor the minority carrier concentrations shown in the figureabove.
There are three modes of operation we must consider
Forward-active (B-E FB, B-C RB) Cut-off (B-E RB, B-C RB) Saturation (B-E FB, B-C FB)
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
19/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 19
BJT biasing modesBJT biasing modes
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
20/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 20
In the cut-off region, the base emitter and
collector base junctions of transistor are
reverse biasedIC IE 0
CutCut--off defined as region of characteristics Ioff defined as region of characteristics ICC = 0= 0
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
21/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 21
Saturation- region defined as region of
characteristics left of VCB = 0 and IC increase
exponentially with VCB increases toward 0
In the saturation region region, the base
emitter and collector base junctions of
transistor are forward biased
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
22/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 22
Active - region defined as region of
characteristics right of VCB
= 0 and IC
first
increases exponentially with VCB increases
toward 0.7 V in Si transistor and then
becomes constant
In the active region region, the base emitter andcollector base junctions of transistor are forward
and reversed biased respectively IC IE 0and is in mA IC
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
23/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 23
Operation in theforward-active
mode
B-E junction is forward biased so
electrons
can be injected from the emitter to the
base, B-C
junction is reverse biased.
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
24/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 24
4.4. TransistorTransistor ConstructionConstruction
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
25/29
2008Junction Transistor Unit 4 Lesson 1-
" , Raj Kamal,
25
BJT structure - three regions, two p-n junctions, threeterminals (emitter, base, collector)
ThinThin
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
26/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 26
ConstructionConstruction
Devices can be p-n-p, or n-p-n structures
Width of the base is small compared to the
minority carrier length and is about 1/150 of
total width, number of free carriers aresmall as doping level is 1/10 th or less
compared to collector)
Emitter is normally heavily doped, thecollector has light doping
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
27/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 27
SummarySummary
We learnt
(i) pnp transistor
(ii) npn transistor (iii) Current Components
(iv) Three configurations-
Common base, common emitter
and Common collector
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
28/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 28
We learnt
(v) Three regions- cut-off,
saturation and active
(vi) Transistor construction
-
8/22/2019 n Pn Pnp Transistor Lesson 01 A
29/29
2008 Junction Transistor Unit 4 Lesson 1- " , Raj Kamal, 29
End of Lesson 1End of Lesson 1
top related