4.3 Understanding Transistors

13
ELECTRONICS

Transcript of 4.3 Understanding Transistors

Page 1: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 1/13

ELECTRONICS

Page 2: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 2/13

Consists of a specially treated semiconductor crystal

Has 3 terminal instead of 2 Emitter (E), base (B) and collector (C)

Can link 2 separate circuits current through one circuit controls currentthrough other.

2 types n-p-n transistors and p-n-p transistors

Page 3: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 3/13

Understanding Transistors

Consists of a specially treated semiconductor crystal

Has 3 terminal instead of 2 Emitter (E), base (B) and collector (C)

Can link 2 separate circuits current through one circuit controls currentthrough other.

2 types n-p-n transistors and p-n-p transistors

Page 4: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 4/13

Page 5: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 5/13

The n-p-n Transistors

Consists a layer of p-type semiconductor sandwiches between 2 layers of n-typesemiconductors.

n-type layers emitter and collector

p-type layer base

Current flows from C to E

Page 6: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 6/13

The p-n-p Transistors

Consists of a layer of n-type semiconductor sandwiched between 2 layers of p-type semiconductors.

P-type layers emitter and collector

N-type layer base

Current flows from E to C

Page 7: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 7/13

Functions & Junctions in a Transistor

 A transistor has 2 p-n junctions

 Acts as a diode.

Terminal FunctionEmitter (E) Supply charge carriers to C

Collector (C) Receive charge carriers from E

Base (B) Control the flow of charge carriersfrom E to C

Page 8: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 8/13

The Flow of Current in a Transistor

Emitter-base junction forward biased

Base-collector junction reverse biased

2 parts to a transistor circuit base circuit & collector circuit Base current, IB  current flows in a base circuit

Collector current, IC  current flows in a collector circuit

Page 9: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 9/13

Consider an n-p-n transistor in a circuit… 

Switched on base-emitter junction is forward biased

Depletion layer narrows its resistance lowers

Cause majority charge carriers (e) in n-semiconductor to flow from E to B.

Number of holes in depletion layer also decreased

Few electrons combine with holes, some remaining electrons flow back into the basecircuit and the rest into the collector circuit.

Base-collector is reverse biased

Electrons cannot flow from collector terminal to the base terminal.

Instead, electrons are attracted across the base-collector junction due to ahigher potential difference at collector terminal.

Flow of current to collector collector current, IC

Page 10: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 10/13

•Bulb X and Y connected to a circuit with n-p-n transistor.

• Variable resistor, RB in the base circuit to control the amount of basecurrent, IB

Page 11: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 11/13

Page 12: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 12/13

Page 13: 4.3 Understanding Transistors

8/4/2019 4.3 Understanding Transistors

http://slidepdf.com/reader/full/43-understanding-transistors 13/13