chapter 2 transistors (bjt)

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Guangdong Institute of Education ---Guangdong Institute of Education ---BTEC electronicBTEC electronic

Electronics chapter 2 transistors

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chapter 2 transistors (BJT)

2.1 Transistor classification

2.2 Bipolar junction transistors (BJT) construction

2.3 Transistor action and operating

2.4 Quiescent Operating Point

2.5 Bipolar transistor characteristics

2.6 Transistor parameters

2.7 Current gain

2.8 Typical BJT characteristics and maximum ratings

2.9 Transistor operating configurations

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exercise

1.Explain,with the aid of sketches,the operationOf an n-p-n transistor and also explain why theCollector current is very nearly equal to the emittercurrent.2.Describe the basic principle of operation of aBipolar junction transistor,including why majoritycarriers crossing into the base from the emitterPass to the collector and why the collector currentIs almost unaffected by the collector potential.

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3.Explain what is meant by ‘leakage current’ in a

Bipolar junction transistor and why this can usually

beignored.

4.For a transistor connected in common-emitter

configuration,sketch the typical output characteristics

Relating collector current and the collector-emitter

voltage,for various values of base current.Explain

The shape of the characteristics.

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5.Sketch the typical input characteristic relating baseCurrent and the base-emitter voltage foratransist orConnected incommon-emitter configuration andExplain its shape.6.With the aid of a circuit diagram,explain howThe input and output characteristic of a common-Emitter n-p-n transistor may be produced.7.Define the term ‘current gain’for a bipolar junctionTransistor operating incommon-emitter mode.

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8.Abipolar junction transistor operates with a col-

Lector current of 1.2A and abase current of 50mA.

What will the value of emitter current be?

[1.25A]

9.What is the value of common-emitter current

gain for the transistor in problem 8? [24]

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chapter 2 transistors (F.E.T)

3.0 Exercise

3.1 Field effect transistor classification

3.2 Field effect transistor construction

3.3 N-type junction field effect transistor operating

3.4 Field effect transistor characteristics

3.5 Typical F.E.T. characteristics and maximum ratings

3.6 M-O-S field effect transistor




3.1 Transistor classification

NPNbiplor junction transistor

PNP

(p-n-p) n-type J.f.e.t.J.f.e.t.

(n-p-n) p-type J.f.e.t.

transistor

field effect transistorn-type depletion-type m.o.s.f.e.t

depletion-type m.o.s.f.e.tp-typ

m.o.s.f.e.t

e depletion-type m.o.s.f.e.t

n-type enhancement-type m.o.s.f.e.tenhancement-type m.o.s.f.e.t

p-type enhancement-type m.o.s.f.e.t




Field effect transistors are available in two basic forms;

Junction gate and insulated gate. The gate source junction

Of a junction gate field effect transistor(JFET) is effectively are verse-biased p-n junction.The gate connection

Of an insulated gate field effect transistor(IGFET).




3.2 The junction field-effect transistor(j.f.e.t.)

Figure Conformation of N channel J.F.E.T




Figure Symbol of JFET

N channel JFET P channel JFET




3.3 The junction field-effect transistor operating

Figure Operation of N channel JFET




3.4 j.f.e.t. characteristics




3.5 Typical F.E.T. characteristics and maximum ratings




3.6 Metal-oxide-semiconductor field-effect transistor

3.6.1 depletion-type MOS FET

N channel P channelConstruction of N channel depletion-type MOS FET




3.6 Metal-oxide-semiconductor field-effect transistor

Figure depletion-type MOS FET

3.6.2 Enhancement-type MOS FET

N channel P channelConstruction of N channel enhancement-type MOS FET




principle of N-channel enhancement m.o.s.f.e.t




Input character and output character




principle of N-channel depletion m.o.s.f.e.t




Assignment 1

R110kΩ

R210kΩ

R3240Ω

R41kΩ

RL

C1

4.7uF

C2100uF

C3

47uF

VCC

12V

IO1IO1

IO2

IO3

IO4

IO3

0

Q1

2N914

10

9

1

R5

470kΩKey=A

50% VCC

2

Ui

Uo

Ii

Io

IC(mA) VCE(V) IB=20(μA) IB=40(μA) IB=60(μA)

2 0.8 2.85 4.6

4 0.9 3 4.9 6 1.0 3.1 5.1

8 1.1 3.2 5.3 10 1.3 3.3 5.5

Tasks:

(Pass Criterion 2.1) Analyse the operation of different types of amplifier. In the wireless receiver customer provided, the audio-frequency input stage amplifier and the audio-frequency power amplifier are given below.

（Ⅰ） The audio-frequency input stage amplifier is show in figure 1.1. The relationships between collector current and collector voltage, with fixed values of base current, are given in table 1.1. You should make IEQ=4mA through adjusting R5, and take this point as its quiescent operating point, then measure the value of R5 and VCEQ.

( ) Draw the static output characteristics of the ⅰtransistor, use these to determine the d.c. current gain and the a.c. current gain at the quiescent operating point.

( ) The resistance value of the load is vague with age. ⅱYou should choose a certain value between 1.2 KΩ to 3 KΩ and draw the d.c. load line and a.c. load line at the static output characteristics.

( ) According to the a.c. load line, determine the ⅲmaximum non-distortion voltage value of the a.c. output signal.

chapter 2 transistors (bjt)

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