Transistors

2. INTRODUCTION
 Transistor is a three terminal electronic
device, made up of semiconductor material
which generally consist of three parts.
i. Base
ii. Emitter
iii. Collector

3. PARTSOFTRANSISTOR
 Emitter:-It is of moderate size and it’s heavily
doped. it’s main function is to supply majority
charge carriers.
 Collector:-It is larger in size and it’s moderately
doped. It’s main function is to collect majority
charge carriers.
 Base:-It’s the middle section of the transistor
and very lightly doped,thin in size.It’s main
function is to reduce the recombination of
charge carriers within base.

4. TRANSISTORS (NPN , PNP)
n p n
E
c
Cross Section B
P N P
Cross Section
(NPN)
E
B
(PNP)
c
Schematic Symbol Schematic Symbol
E
E
B
B
c
c

5. TRANSISTOR WORKING PRINCIPLE
The transistor can function as:
An insulator
A conductor
The transistor's ability to fluctuate between these two
states enables it to switch or amplify.

6.  Biased transistor:-A biased transistor
means a transistor which is connected with
external voltage source.

7. CONNECTION CONFIGURATION OF TRANSISTOR
 Common base configuration.
 Common Emitter configuration.
 Common Collector configuration.
 Common base
configuration

8. CONNECTION CONFIGURATION OF
TRANSISTOR
 Common Emitter
configuration.
 Common Collector
configuration.

9. WORKING REGION OF TRANSISTOR
Region Emitter Base Junction Collector Base
Junction
Active Forward biased Reverse biased
Cut-off Reverse biased Reverse biased
Saturation Forward biased Forward biased
 A biased transistor works in three region:-

10. OPERATION OF N-P-N TRANSISTOR
 Base to Emitter junction is forward biased
by the dc sourcBeE v .
 Collector to base junction is reverse
biased by the dc CsEource v .
 The forward biased EB junction causes
the n type emitter electrons to flow
towards base.This constitute emitter
current.
 Some electrons combine in base region
and constitute base current.
 Remaining electrons cross base region
and move through collector region and it
constitute collector current.

11. OPERATION OF P-N-P TRANSISTOR
 Base to Emitter junction is forward
biased by the dc sourceBvE .
 Collector to base junction is
reverse biased by the dcCEsource v
.
 The forward biased EB junction
causes the p type emitter hole to
flow towards base.This constitute
emitter current.
 Some hole combine in base region
and constitute base current.
 Remaining hole cross base region
and move through collector region
and it constitute collector current.

12. TRANSISTOR CURRENT
I
IB
IB
IE
IC
IC
E
npn
IE = IB + IC
pnp
IE = IB + IC

13. TRANSISTOR VOLTAGE
v
v
CB
BE
vCE
VC
B
• v
• CE
•vBE
•pnp
• VCE = -VCB + VBE

14. CURRENT GAIN

15. TRANSISTOR OPERATION
Operation Region Bias Application
CUT OFF REGION IB and Ic are 0 (base-
emitter and collector –
base junction is reverse
biased)
Open Switch (OFF)
SATURATION REGION Base emitter junction is
forward biased; IB flows
Closed Switch (ON)
ACTIVE REGION B-E junction is forward
biased but C-B junction
is reverse biased;
Amplifier

16. TRANSISTOR AS A SWITCH

17. ON MODE