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Regions of a Transistor A Bipolar Junction Transistor is a three terminal device containing 3 regions: Emitter, Base and Collector.

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Presentation on theme: "Regions of a Transistor A Bipolar Junction Transistor is a three terminal device containing 3 regions: Emitter, Base and Collector."— Presentation transcript:

1 eCourseware@AIKTC

2 Regions of a Transistor

3 A Bipolar Junction Transistor is a three terminal device containing 3 regions: Emitter, Base and Collector.

4 THE TRANSISTOR There are two types of (bipolar junction) transistors, npn and pnp Bipolar transistor symbols

5 NPN vs PNP NPN and PNP function the same way Power supply polarities are reversed For NPN, positive supply is used NPN has higher frequency response as electrons are the charge carriers. NPN is more widely used

6 A transistor consists of two PN junctions. Thus a transistor is like two PN – junction diodes connected back to back.

7 2.2 Packages Examples of transistor packages

8 Transistor Packages (low power & high power)

9 2.4 Transistor Configurations common emitter (CE) common base (CB) common collector (CC).

10

11 Currents in CE Circuit

12 2.5 Emitter, collector and base currents

13 In the CE configuration:

14 Transistor Operation Regions Operation Region BiasApplication CUT OFF REGION I B and I c are 0 (base-emitter junction is reverse biased) Open Switch (OFF) SATURATION REGION Base emitter junction is forward biased; I B flows Closed Switch (ON) ACTIVE REGION B-E junction is forward biased but C- E junction is reverse biased; Amplifier

15 Transistor Applications: Transistor can act as a Switch

16

17 Transistor Applications Switch Amplifier Oscillator

18 Transistor as a Switch Light operated switch Darkness operated switch Digital Logic Gates Switching power supply

19 Transistor as a Variable Resistor Amplifier Oscillator Modulator Detector

20 Light Failure Warning System using Transistor as a Switch

21 Light Failure Warning System In this, the transistor is used as a switch LDR is a light dependant resistor. It is a light sensor. When it is dark, LDR resistance increases; base current flows; the transistor becomes ON and relay switches. So the bell rings.


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