Amplifiers, Oscillators, Microelectronics - TIP

6/21/2014

One person with a is equal to a force of 99 who have only . - John Stuart Mill, 1806-1873

Amplifiers

Amplifiers Fernando Victor V. de Vera ECE, M.Tech

AMPLIFIER General Presentation

• An electronic circuit which is capable of

increasing the signal magnitude or amplitude without appreciably altering the signal waveform characteristic. • AMPLIFICATION is the process of providing an increase in amplitude.

Classifications of Amplifiers

Classifications • • • • • • • •

Voltage Amplifier

Voltage Amplifier – Voltage-controlled voltage source Current Amplifier – Current-controlled current source Transconductance Amplifier – Voltage-controlled current source Transimpedance Amplifier – Current-controlled voltage source VoltageAmplifier

Current Amplifier

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Current Amplifier

Transconductance Amplifier

Transconductance Transconducta nce Amplifier

Transimpedance Transimpedance Amplifier

TransimpedanceAmplifier

AMPs Classifications - Summary

Summary

Types of Amplifiers • Amplifiers by Function • Amplifiers by Frequency Response

RQS – No. 3

Amplifiers by Function • VOLTAGE

• POWER

AMPLIFIER

AMPLIFIER

– The type of

– Type of amplifier

amplifier in which the output signal voltage is larger than the input signal voltage.

in which the output signal power is larger than the input signal power. The secret of success is constancy to purpose. Benjamin Disraeli

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Audio Amplifier

Amplifiers by Frequency Response

• Audio amplifiers are designed to amplify

signals with frequency between 15 Hz and 20 kHz. • Any amplifier that is designed for any band of frequencies contained in AUDIO RANGE is called Audio Amplifier.

• Audio Amplifier • RF Amplifier • Video Amplifier

RF Amplifier • RF Amplifiers are designed to amplify

signals with frequencies between 10 kHz and 100 GHz. • Any Amplifier designed to amplify frequency band included in the RF range is considered an RF Amplifier.

Video Amplifier AMPLIFIERS. • Also known as WIDEBAND AMPLIFIERS. • A Video Amplifier is designed to amplify a band of frequencies from 10 Hz to 6 MHz.

Question  An audio amplifier operates in the

frequency range of

>>Bringing You Forward

POSSIBLE BOARD QUESTIONS

A. B. C. D.

0 to to 20 20 H Hzz 20 Hz to to 20 20 kHz kHz 20 to 200 200 kHz kHz Above Above 20 kHz

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Question

 Which of the following refers to the gain

 A tuned RF amplifier is

A. B. C. D.

Question of a circuit?

Narro Narrowb wband and Wide Wideba band nd Direct Direct coupled coupled Impedan Impedance ce coupled coupled

A. Input quantit quantity y of an amplifier amplifier divided by by the output quantity. B. The difference difference between between the input input voltage voltage and the output voltage of a circuit. C. The ratio ratio of the output output quantity quantity to to input quantity of an amplifier. D. The total increase increase in in output quality quality over over the input quantity of an amplifier.

Question  Which of the following is a

transconductance amplifier? A. B. C. D.

OP-A OP-AMP MP BJT FET Vara Varact ctor or

Question  Which of the following is a current

amplifier? A. B. C. D.

OP-A OP-AMP MP BJT FET Varac Varacto torr

Amplifier Classes • The class of operation of an amplifier is

determined by the amount of time – in relation to the input signal – that current flows in the circuit. >>Bringing YOU Forward

AMPLIFIER CLASSES

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Amplifier Classes • • • •

Class A Amplifiers

Class A Class B Class AB Class C

• The amount of the

output signal flow varies for full 360 degrees of the cycle. • Class A amplifier has a characteristic of GOOD FIDELITY and low EFFICIENCY.

Class A amplifier

Class A Amplifier

Class A - Grapical

Class B Amplifier

Class !

Class B Amplifier

• The amount of the

output signal flow is 180 degrees. • Class B amplifiers is twice as efficient as Class A amplifiers. • Class B amplifiers is used in cases where exactly 50% of the input signal is amplified. Class ! - Grapical

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Class B Amplifier

Class AB Amplifier • The output signal

flows for more than 180 degrees but less than 360 degrees. • Class AB amplifiers have better efficiency and poorer fidelity than Class A amplifiers.

Class A!

Class AB Amplifier

Class AB Amplifier

Class A! - Grapical

Class C Amplifier

Class C

Class C Amplifier

• Class C amplifier

operates on less than 50% of the input signal. • Class C amplifier has the BEST EFFICIENCY but WORST FIDELITY.

Class C - Grapical

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Class C Amplifier

Summary of Amplifier Classes

C"ASS#S of Amplifiers – Ta$le of Comparison

CLASSES of Amplifiers Comparison Class A

Class B

Class AB

Class C

Active region (linear portion)

Cut-off region

a little above cut-off

below cut-off

Conduction Angle

360O

180O

Between 180O – 35O

le!! t"an 180O

Distortion

low

"ig"

#o$erate

ver% "ig"

Maximum Efficiency

&5'  50' for tran!for#er couple$

8*5'

Between Cla!! B an$ A

#ore t"an 0'

Q-point position



RQS – No. %

Question  A characteristic of an amplifier which

refers to how much of its supply power is delivered to the load. A. B. C. D.

Output Output RMS power power Output Output DC power power Effi Effici cienc ency y Clas Classs A

Question  Which class of amplifier has the highest

linearity and least distortion? A. B. C. D.

Clas Classs A Class lass C Clas Classs AB Clas Classs B

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Question  Which class of amplifier is

distinguished by the presence of output throughout the entire signal cycle and the input never goes into cutoff region? A. B. C. D.

Clas Classs A Class lass C Class lass B Clas Classs D

Question  For maximum peak-to-peak output

voltage, the Q point should be A. B. C. D.

Near satura saturatio tion n Near Near cut cutof offf At the the center center of the dc dc load line At the center of the the ac load load line

Question  Class C amplifiers are almost always

A. B. C. D.

Transformer-c Transformer-coupled oupled between between stages stages Operated Operated at at audio audio frequencies frequencies Tuned Tuned RF RF ampli amplifie fiers rs Wide Wideba band nd

Question  With class A, the output

A. B. C. D.

Uncl Unclip ippe ped d Clipped Clipped on positive positive voltage voltage peak peak Clipped Clipped on negative negative voltage voltage peak peak Clipped Clipped on negative negative current current peak peak

Question  The bandwidth of a class C

amplifier

decreases when the A. B. C. D.

Resonant Resonant frequen frequency cy increases increases Q incre increas ases es XL decr decreas eases es Load resistance resistance decreases decreases

signal should be

Question  Complementary push-pull transistor

uses ___ transistors. A. B. C. D.

PNP PNP and and NPN NPN Darlington Darlington and feedback feedback pair Both Both NPN NPN FET FET and and BJT BJT

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Question  Push-pull is almost always used with

A. B. C. D.

Question  One advantage of a class B push-pull

amplifier is

Clas Classs A Class lass B Class lass C All of the the above above

A. B. C. D.

Other Amplifiers - Circuit Configurations output of • CASCADED AMPLIFIER – the output the first stage provides the input of the next stage (connected in a series fashion) • CASCODE AMPLIFIER – a commonemitter on the first stage feeding a common-base stage. This provides high input impedance and low noise.

&ter Amplifiers - Circuit Configurations

Very small small quiescent quiescent current drain Maximum Maximum efficienc efficiency y of 78.5 78.5 percent percent Greater Greater efficienc efficiency y than than class class A All of the the above above

Other Amplifiers - Circuit Configurations • DARLINGTON AMPLIFIER – two

transistors in which the collectors are tied together and the emitter of the first transistor is directly coupled to the base of the second transistor. The current gain β of this circuit is the product of the individual transistors’ current gain. Also called DARLINGTON PAIR, PAIR, DOUBLEEMITTER FOLLOWER, FOLLOWER, or β MULTIPLIER MULTIPLIER.. &ter Amplifiers - Circuit Configurations

Other Amplifiers - Circuit Configurations • DIFFERENTIAL AMPLIFIER – designed to

respond to the difference between the two input voltages. Differential amplifier is usually the input circuit of most lownoise power amplifiers and operational amplifiers.

>>Bringing YOU Forward

COUPLING

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Coupling • The process of transferring energy from

one circuit to another is called COUPLING.

Direct Coupling • The method of coupling with the least

number of circuit elements. • In direct coupling, the output of one stage is directly connected to the input of the following stage.

Direct Coupling

Types of Coupling • • • •

Direct Coupling RC Coupling Impedance Coupling Transformer Coupling

Direct Coupling • Direct Coupling provides a GOOD

FREQUENCY RESPONSE since no frequency-sensitive frequency-sensitive devices are present. • Disadvantages includes: – High Voltage requirement for the

succeeding stages, – It is difficult to match the impedance from stage to stage with direct coupling. – Not very efficient therefore losses increase as the number of stages increases.

RC Coupling • RC Coupling is the most used coupling in

amplifiers. • RC coupling allows the coupling of the signal while it isolates the biasing of each stage. • Disadvantage includes: LOW EFFICIENCY because of the resistor use dc power.

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RC Coupling

Impedance Coupling • Impedance Coupling is very similar to RC

coupling, the only difference is coil is used instead of resistor. • Impedance Coupling has better efficiency because of the small coil resistance used instead of a resistor in RC coupling.

Impedance Coupling

Transformer Coupling • In Transformer Coupling, inductors are

used in the primary and secondary therefore its more efficient. • Transformer Coupling Coupling is used for the final output because of the impedance matching qualities of the transformer.

Transformer Coupling



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Question  A passive device used for

phase-splitting

of a signal. A. B. C. D.

Trans Transfo forme rmerr OP-A OP-AMP MP Voltage Voltage divider configurati configuration on All All of the these se

Questi on

 If three amplifiers with a gain of 8 each

are in cascade, how much is the overall gain? A. B. C. D.

72 512 24 8

Question  The current in a coupling circuit for high

frequencies is A. B. C. D.

Question  A coupling capacitor is ___.

A. B. C. D.

Zero Maxi Maximu mum m Mini Minimu mum m Aver Averag age e

A dc dc sho short rt An ac open open A dc open open and and an ac short short A dc short and an ac open open

Question  A disadvantage of transformer coupling,

as opposed to capacitive coupling, is that: A. Transformers Transformers can’t match match impedance impedances. s. B. Transformers Transformers can’t work above above audio audio frequencies. C. Transf Transforme ormers rs cost cost more. D. Transformers Transformers reduce the gain. gain.

Question

Question  An advantage of impedance coupling

compared to RC coupling is __. A. B. C. D.

Higher Higher effic efficienc iency y Lower Lower powe powerr Low Low heat heat Less distor distortio tion n

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Question  A disadvantage of RC coupling is ___.

A. B. C. D.

Low Low powe powerr High High effici efficienc ency y Low Low effici efficien ency cy High High distorti distortion on level level

>>Bringing YOU Forward

DIFFERENTIAL AMPLIFIERS

Differential Amplifiers

Common Emitter and Common Base Configuration

• An amplifier that operates with two

possible inputs and two possible outputs. • It operates on the difference between two inputs.

The Basic Differential Amplifier • If Common-Emitter

and Common-Base Configuration is combined, the basic Differential Amplifier is formed.



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Question  A differential amplifier ___.

A. B. C. D.

Is a part part of an op-am op-amp p Has two output outputss Has one input input and one one output output a and b are correct correct

Question  Differential amplifier in the

mode ___. A. Opposite Opposite polarity polarity signals signals are applied applied to the inputs B. The gain is unity unity C. The outputs outputs are different different amplitudes amplitudes D. Only one one supply supply voltage voltage is is used

Question  Differential gain is ___.

A. B. C. D.

Question  When the two input terminals of a diff

Very Very high high Very ery llow ow Dependent Dependent on the the input input voltage voltage Abou Aboutt 100 100

amp are grounded, A. B. C. D.

Question  One source of output error voltage is

A. B. C. D.

differential

Input Input bias bias curren currentt Difference Difference in collecto collectorr resistors resistors Tail Tail cur curren rentt Common-mod Common-mode e voltage voltage gain

The base base currents currents are are equal equal The collecto collectorr currents currents are equal equal An output output error voltage voltage usually usually exists exists The ac output output voltage voltage is zero zero

Question  An amplifier basically constructed from

two transistors and whose output is proportional to the difference between the voltages applied to its two inputs. A. B. C. D.

differ different ential ial amplifier amplifier cascod cascode e ampl amplifi ifier er comple complemen mentary tary amplifi amplifier er quasi-comple quasi-complementary mentary amplifier amplifier

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Operational Amplifiers • It is an amplifier which is designed to be

used with other components to perform either computing functions or some type of transfer operation such as filtering. >>Bringing YOU Forward

OPERATIONAL AMPLIFIERS (OP-AMPS)

Characteristic of Op-Amp

Block Diagram of Op-Amps

• Very High Gain • Very High Input

Impedance • Very Low Output Impedance • Very Wide Bandwidth

Slew Rate

OP-AMP AC Consideration

• The maximum rate of change of the

output voltage in response to a step input voltage. • The slew rate is dependent upon the high-frequency response of the amplifier stage within the op-amp.

Guessing Time

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Common-Mode Rejection Ratio (CMRR)

OP-AMP CMRR

• The measure of an amplifier’s ability to

reject common-mode signals. • It is the ratio of the open-loop gain of and the common-mode gain of the Opamp.

AC Considerations-'nity Gain !( )roduct

OP-AMP Circuit Configurations • • • • • • •

Inverting Non-Inverting Voltage Follower Summing Subtractor Integrator Differentiator

Inverting Configuration • The input signal is

connected to the inverting input of the Op-Amp. • The output signal is inverted with respect to the input.

INVERTING Amplifier

Non-Inverting Configuration • The input signal is

directly connected to the inverting input of the Op-Amp. • The output is Inphase with the input.

Non-*n+ertingAmplifier

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Non-INVERTING Amplifier

VOLTAGE FOLLOWER

V&"TAG# V&"TA G# ,olloer

Summing Amplifier

Summing Amplifier

SUMMING Amplifier

• The output level is

determined by adding the input signals together although the output signal will be the opposite polarity compared to the sum of the input signals.

S'!TRACT&R or *,,#R#NC*NG Amplifier

SUBTRACTOR or Differencing Amp

INTEGRATOR INTEGRATOR Circuit

*NT#GRAT&R

*,,#R#NT*AT&R

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DIFFERENTIATOR DIFFERENTIATOR Circuit

OP-AMP as a COMPARATOR

!ac/ to &)-A0) #lectrical Caracteristics

C0RR

Question  An integrated IC OP-AMP normally has

___.



A. B. C. D.

Two inputs inputs and two output output Two input inputss and one outpu outputt Single output and single input Eigh Eightt pins pins

Question  Which of the following characteristics

does not apply to an op-amp? A. B. C. D.

High High gai gain n High High input input imped impedanc ance e Low Low pow power er Low input input impe impedan dance ce

Question An application of an operational amplifier in which the output signal is determined by the sum of the input signals multiplied by the gain; Eout = Gain(E1+E2+…) A. B. C. D.

magnet magnetic ic amplif amplifier ier summin summing g ampli amplifie fierr differ differenc ence e amplifi amplifier er scalin scaling g amplifi amplifier er

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Question  What is the ideal value of

A. B. C. D.

CMRR?

Zero Nega Negati tive ve Infi Infini nite te One

If the mind keeps thinking “You've had enough” But the heart keeps telling t elling you “Don't give up” Who are we to be questioning, Wondering “what is what?” Don't give up, through it all JUST STAND UP! - From the song “Just stand Up”

OSCILLATORS • Oscillator is a circuit that produces a

Oscillators Fernando Victor V. de Vera ECE, Master of Technology (MT) [email protected] [email protected]

Conditions for Oscillation

periodic waveform on its output with only the dc supply voltage as an input. !C

Oscillator

Conditions of Oscillation: The BARKHAUSEN CRITERION

• The phase shift around the feedback

• To start oscillation,

loop must be effectively 0 or 360 degrees. • The voltage gain around the closed loop feedback loop (loop gain) must equal to 1 (unity).

• To sustain

Loop Gain >1

oscillation, Loop Gain = 1

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Conditions of Oscillation: The BARKHAUSEN CRITERION • Damping –

LoopGain<1

• Clipping –

LoopGain>1

Oscillators Stability Requirement • Amplitude Stability – refers to the ability

of the oscillator to maintain a constant amplitude in the output waveform. • Frequency Stability – refers to the ability of the oscillator to maintain its operating frequency.

• Steady Oscillation –

LoopGain=1

Factors Affecting Stability • Short-Term Stability Load – Load Bias – Bias • Long-Term Stability Component Characteristic – Component (component aging, changes in temperature and humidity)

Components of Oscillator • Amplification • Frequency Determining Device • Regenerative Feedback

Classification of Oscillators • Sinusoidal • Non-Sinusoidal

PROBABLE BOARD QUESTIONS…

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Probable Board Question No.1:

Probable Board Question No.2:

• Which condition must exist for a circuit

• Which of the following is not an essential

to oscillate?

part of an oscillator?

– A. It must have a negative feedback

– A. source of energy that supply the losses in

sufficient to cancel the input – B. It must have a gain of less than 1 – C. It must have a positive feedback sufficient to overcome losses – D. It must be realized

tank circuit. – B. a resistor IC combination circuit – C. resonant circuit consists of inductance and capacitance – D. regenerative feedback circuit

Sinusoidal Oscillators • A sinusoidal oscillator is a device that

produces a sine-wave output signal. • The output of a sinusoidal oscillator

SINUSOIDAL OSCILLATORS

38

Filters and Oscillators

What should be the phase

shift around the feedback loop in order to oscillate? a.90 a. 90 degrees degrees b.180 degrees c. 270 degrees degrees d.360 degrees

should be constant in amplitude and frequency.

39


The attenuation of the

feedback circuit is 0.2. What should be the gain of the amplifier? a. 20 200 0 b.20 c. 50 d.5

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42


What should be the closed

loop voltage gain of an oscillator to start up? a.1 b.>1 c. <1 d.0

45


The voltage that starts an

oscillator is caused by a. Ripple from the the power supply b.Noise voltage in resistors c. The input input signal signal from a generator d.Positive feedback

Types of Sinusoidal Oscillator • RC Oscillators • LC Oscillators

RC OSCILLATORS

• Crystal-Controlled Oscillator

RC Oscillators • Wein-Bridge Oscillator • Phase Shift Oscillator

Wein-Bridge Oscillator • A Wein-Bridge

Oscillator is a leadlag circuit. • Lead-Lag circuit attenuation = 1/3

• Twin-T Oscillator

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Wien-Bridge Oscillator

Phase-Shift Method • The three RC circuits in the feedback

loop can provide a maximum phase shift approaching 90 degrees. • Oscillation occurs at the frequency where the total phase shift through the RC circuits is 180 degrees. • Feedback circuit attenuation = 1/29

Phase-Shift Method

Phase Shift Oscillator • R1=R2=R3=R • C1=C2=C3=C

Twin-T Oscillator

Twin T Oscillator

• One of the twin-T filters has a low-pass

response and the other has a high-pass response. • The combined parallel filters produce a bandstop or notch response with a center frequency equal to the desired frequency of oscillation.

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46


What is the circuit used in

the feedback of a Wienbridge oscillator? a.Lead-lag b.LC c. RL d.RC

48

47


The attenuation of a lead-

lag circuit used in a wien bridge oscillator. a.3 b.1/3 c.1 d.0


The Wien-bridge oscillator

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A lag circuit has a phase

is useful

angle that is

a.At low frequencies b.At high frequencies c. With LC tank tank circuits circuits d.At small input signals

a. Between 0 and +90 degrees b.Greater than 90 degrees c. Between Between 0 and -90 -90 degrees d.The same as the input voltage

56


Oscillation occurs in a phase-

shift oscillator when the phase shift through the feedback path is ___. a. 90 degrees degrees b.180 b. 180 degrees degrees c. 27 270 0 degrees degrees d.360 d. 360 degrees degrees

58


How many RC circuits are

usually used in a phaseshift oscillator? a.1 b.2 c.3 d.5

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LC Oscillator • A type of oscillator that has a

combination of inductor and capacitor. • LC feedback elements are normally used in oscillator that require higher frequencies of oscillation (f>1MHz).

LC OSCILLATORS

Types of Feedback for LC Oscillators

Types of LC Oscillator • • • •

Armstrong Oscillator

Armstrong Oscillator Hartley Oscillator Colpitts Oscillator Clapp Oscillator

Armstrong Oscillator

• Armstrong Oscillator is used to produce a

sine-wave output of constant amplitude and a fairly constant frequency within the RF range. • It uses an LC circuit to establish the frequency of oscillation. • It uses Class C amplifier with self-bias. • Its frequency is fairly stable, and amplitude relatively constant.

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Hartley Oscillator

Hartley Oscillator

• Hartley Oscillator is an improvement of

Armstrong Oscillator. • Hartley Oscillator can generate a wide

range of frequencies and very easy to tune.

Colpitts Oscillator

Colpitts Oscillator

• Colpitts Oscillator is similar to Hartley

Oscillator except that two capacitors are used in the tank circuit instead in stead of a tapped coil. • Colpitts Oscillator has fairly good frequency stability, stability, easy to tune and can have a wide range of frequencies.

Clapp Oscillator

Clapp Oscillator

• Clapp Oscillator is a variation of Colpitts

Oscillator. • The basic difference is an additional

capacitor Cs in series with the inductor in the resonant feedback circuit.

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65


For frequencies greater

than 1MHz, what types of oscillators are used? a.LC b.RC c. Phase-shi Phase-shift ft d.Wien-bridge

68


Q of the coil increases, what happens to the resonant frequency? a. Remains Remains constant constant b.Increase c. Decrea Decrease se d.Stabilize


A self-excited oscillator in

which the tank circuit is divided into input and feedback portions by an inductive voltage divider. a. Clap Clapp p b. Armstro Armstrong ng c. Collp Collpits its d. Hartley Hartley


Colpitts oscillator contains a

tank circuit in its feedback circuit with how many capacitors and inductors? a. 2, 1 b.1, 2 c. 1, 1 d.2, 2

In a Colpitts oscillator, as the

71

67

69


What do you call the

oscillator circuit that uses tapped coil in the tuned circuit? a. Clapp Clapp b.Armstrong c. Collpi Collpits ts d.Hartley

72


A variation of the collpits

oscillator that makes use of series resonance rather than parallel. a. Clapp Clapp b.Armstrong c. Modified Modified Collpits Collpits d.Hartley

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73


Armstrong oscillator uses

what coil? a.Tapped coil b.AF transformer coil c. Tickler Tickler Coil d.Magnetic coil

Common Crystals

Piezoelectric Effect • Crystal vibrates at a constant rate when

it is exposed to an electric field. • The physical dimensions of the crystal determine the frequency of vibration. • Cutting the crystal to specific dimensions can produce crystals that have very exact frequency ratings.

Crystal Controlled Oscillator

• Rochelle salt has the best piezoelectric

properties but is very fragile. • Tourmaline Tourmaline is is very tough, but its vibration rate is not as stable. • Quartz Quartz crystals crystals fall between the two extremes and are the most commonly used. Quartz crystals are made from silicon dioxide (SiO2 ( SiO2). ).

Crystal-Controlled Oscillator

Frequency Response of Crystal Controlled Oscillator

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81


The material with the

piezoelectric effect is


82

a.Quartz b.Rochelle salts c. Tourmali Tourmaline ne d.All the above


Crystals have a very

a.Low Q b.High Q c. Small Small inductance inductance d.Large resistance

Non-Sinusoidal Oscillators • Non-sinusoidal Oscillators generate

complex waveforms such as square, rectangular, trigger, sawtooth and trapezoidal waveforms. • Also called RELAXATION OSCILLATORS.

NON-SINUSOIDAL OSCILLATORS

Periodic Waveforms • A waveform which undergoes a pattern

of changes, returns to its original pattern, and repeats the same pattern of changes is called a PERIODIC waveform.

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Types of Periodic Waveforms

Square Wave

Types of Waveform Generators

Multivibrators • The type of circuit most often used to

• • • •

generate square or rectangular waves is the multivibrator. • Three Types:

Multivibrators Blocking Oscillators Sawtooth Oscillators Trapezoidal Oscillators

• Astable Multivibrator • Monostable Multivibrator • Bistable Multivibrator

Multivibrators: Summary Multivibrator Other Name

Stable States

Timing Needs Capacitors Trigger?

Astable

Clock, Freerunning

0

2

No

Monostable

One Shot, 1 Pulse Regenerator Regenerator

1

Yes

Bistable

Flip-Flop

0

Yes

2


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90


For a BMV, ___.

a. The base resistor resistorss are connected to Vcc b.The feedback is coupled trough two resistors c. The feedback feedback is coupled coupled trough two capacitors d.The base resistors are connected to ground.

94


A two-state circuit that

has zero, one or two stable output states. a.Bistable multivibrator b.Monostable multivibrator c. Astable Astable multivibr multivibrator ator d.Multivibrator

Probable Board Question No.15: • The three types of multivibrators are C. Bistable • A. Astable D. Multistable • B. Monostable – A. A, B, C, and D – B. A, C, and D – C. B, C, and D – D. A, B, and C

91


The trigger pulses in vibrator

circuits ___.

a. Positive and and of sufficient amplitude b.Over rides the negative supply to the base c. Both Both a and and b d.None of these

April 2006 Board Question: • What type of circuit is used to produce

square or rectangular waves? – A. Sinusoidal generator – B. Multi-vibrator – C. Non-sinusoidal generator – D.Wave generator

Probable Board Question No.16: • In an astable multivibrator, which

components determine the pulse repetition frequency? – A. LC coupling networks – B. RC coupling networks – C. direct coupling – D. impedance coupling

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Short History of Microelectronics

MICROELECTRONICS Engr. Fernando Victor V. de Vera BSECE MT

• Integrated Circuits – Monolithic IC: Jack Kilby (1958, Texas Instruments) – Robert Noyce (1959) – Added a metal layer for interconnecting components in the chip.

Microelectronics MICROELECTRONICS is defined as that • MICROELECTRONICS area of technology associated with and applied to the realization of electronic systems made of extremely small electronic parts or elements. • Normally associated with Integrated Circuit (IC), but not only IC’s

1. The area of of technology technology associ associated ated with and applied to the realization of electronic systems made of extremely small electronic parts or elements. a. Miniat Miniaturi urizat zation ion b. Microelect Microelectronic ronicss c. Nanote Nanotechn chnolo ology gy d. Nanoelectr Nanoelectronics onics


2. Which of the following is a problem associated with the use of vacuum tubes? a. Heat Heat b. Long warm-up warm-up time c. High High power power require requiremen mentt d. All of of the above above

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3. Building a system on modules or blocks where each module perform a necessary function of the system. a. b. c. d.

4. An epoxy board on which the circuit leads have been added which reduces weight and eliminates point-to-point wiring a. Mother Motherboa board rd b. PCB c. Integr Integrate ated d circui circuitt d. ProtoProto-boa board rd

Modula Modularr packagi packaging ng Block Block packagi packaging ng Func Functi tion onali ality ty Repa Repair ir

Integrated Circuit (IC) • Consists of elements inseparably

associated and formed on or within a single SUBSTRATE (mounting surface). • The circuit components and all interconnections are formed as a unit.

Limitations of IC Technology Technology • Impractical to create inductor – Inductors = coil • High power devices are not possible – Example: High-Power amplifiers

Advantages of the IC Technology • • • • • •

Compactness High Speed Low Power Requirement Reliability Ease of Maintenance Modular Construction

Linear vs. Digital ICs • LINEAR IC – A linear IC is used to process analog signals such as voices, music, and radio transmissions. – The term “linear” arises from the fact that, in general, the amplification factor is constant as the input amplitude varies.

• DIGITAL IC – A digital IC, also s ometimes called a digital-logic IC, operates using just two states, called high (logic 1) and low (logic 0)

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Types of Linear IC 1. OP-AMP OP-AMP (Operational (Operational Amplifie Amplifier) r) 2. Voltage Voltage Regulator Regulatorss (78xx, 79xx, 79xx, 317, 337, etc) 3. Time Timerr IC 4. Analog Analog Multiplexe Multiplexerr 5. Compar Comparato atorr IC

Digital IC • BIPOLAR Types – TTL (Transistor-Transistor Logic) – ECL (Emitter-Coupled Logic) • MOS (Metal-Oxide Semiconductor) Types – CMOS (Complementary MOS) – NMOS/PMOS (N-Channel MOS/ P-Channel MOS)

Component Density • COMPONENT DENSITY is the number of

elements per chip in an IC. • There is an absolute limit on the component density that can be attained; it is imposed by the atomic structure of the semiconductor material. • A logic gate will never be devised that is smaller than an individual atom.

Small Scale Integration (SSI) • With less than 10 gates per chip. • Example: Basic logic gate packages

(7400, 7404, etc)

Component Density • • • • • •

SSI (Small Scale Integration) MSI (Medium Scale Integration) LSI (Large Scale Integration) VLSI (Very Large Scale Integration) ULSI (Ultra- ) ELSI (Extremely- )

Medium Scale Integration (MSI) • There are 10 to 100 gates per chip. • An advantage of MSI (in a few

applications) is that fairly large currents can be carried by the individual gates. • Both Bipolar and MOS technologies can be adapted to MSI.

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Large Scale Integration (LSI)

Very Large Scale Integration (VLSI)

• There are 100 to 1000 gates per

• Have from 1,000 to 10,000 components

semiconductor chip. • This is an order of magnitude (a factor of 10) more dense than MSI. • Electronic wristwatches, single-chip calculators, and small microcomputers are examples of devices using LSI ICs.

per chip. • This is an order of magnitude more dense than LSI. • Complex microcomputers, and peripheral circuits such as memory storage ICs, are made using VLSI.

Ultra- and Extremely- LSI (ULSI/ELSI) • Have more than 10,000 gates in a chip.

Summary of Component Densities Level of Integration !ensit"#

Number of $ates

SSI (Sall Scale Integration! Integration!

"10

#SI (#e$iu Scale Integration! Integration!

10 % 100

&SI (&arge Scale Integration! Integration!

100 % 1,000

'&SI ('er ('er &arge Scale Integration! Integration!

1,000 % 10,000

)&SI, *&SI ()ltra-, *+treel- &SI!

10,000

14. Allow thousands of elements in a single chip. a. LSI and VLSI VLSI b. Diffu Diffusio sion n c. SSI SSI and and MSI MSI d. Mask Masking ing


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15. Generally applied to integrated circuits consisting of from 1,000 to 2,000 logic gates or from 1,000 to 64,000 bits of memory. a. SSI b. MSI MSI c. LSI d. VLSI VLSI

3 Types of ICs (Based on the Material and Construction) • MONOLITHIC • FILM – Thin Film – Thick Film • HYBRID

16. Used in integrated circuits containing over 2,000 logic gates or greater than 64,000 bits of memory. a. SSI b. MSI c. LSI d. VLSI VLSI

Monolithic IC INTEGRATED CIRCUITS are • MONOLITHIC INTEGRATED those that are formed completely within a semiconductor substrate. • These ICs are commonly referred to as SILICON CHIPS.

Film ICs • 2 Categories: – THIN Film – THICK Film • Film components are made of either

conductive or nonconductive material that is deposited in desired patterns on a ceramic or glass substrate. • Film can only be used as PASSIVE circuit components, such as resistors and capacitors.

Hybrid ICs • HYBRID INTEGRATED CIRCUITS combine

two or more integrated circuit types or combine one or more integrated circuit types and DISCRETE (separate) components.

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47. Microcircuit refers to any component containing what types of elements? a. Microe Microelec lectro tronic nicss b. Integrated Integrated circuits circuits c. Passiv Passive e elem element entss d. Activ Active e elements elements


48. Components made up exclusively of discrete elements are classified as what type of electronics? a. Disc Discre rete te b. Miniat Miniature ure c. Pass Passiv ive e d. Acti Active ve

6. Consist of elements inseparably associated and formed on or within a single substrate. a. Mother Motherboa board rd b. PCB c. Integr Integrate ated d circui circuitt d. ProtoProto-boa board rd

7. Which of the following are classifications of integrated circuits? a. Mono Monoli lith thic ic b. Film Film c. Hy Hyb brid rid d. All of thes these e

8. IC’s that are formed completely within a semiconductor substrate. a. Mono Monoli lithi thicc b. Film Film c. Hy Hyb brid rid d. All of thes these e

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9. Other term for a monolithic IC. a. Silico Silicon n chip chip b. Chip Chip c. Die d. All of thes these e

10. Monolithic IC’s contains: a. Passive Passive elements elements only b. Active Active elements elements only c. Both Both active active and Pass Passive ive d. None None of thes these e

Fernando Victor V. de Vera ECE, Master of Technology

SOLID STATE DEVICES

END OF SESSION

Electrical Classification of Materials

Solid State Devices • Operates by virtue of the movement of

• Conductor • Insulator • Semiconductor

electrons with solid piece of semiconductor material

227

Con"uctor

228

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Conductor • A material with LESS THAN 4 VALENCE

ELECTRONS. • Copper (Cu), Silver (Ag), Gold (Au) and Aluminum (Al)

229

#nsulator

230

Materials Conductivity • • • • •

Silver Copper Gold Aluminum Iron

Insulator

63.01 x 106 S/m 59.60 x 106 S/m 45.20 x 106 S/m 37.80 x 106 S/m 10.44 x 106 S/m

VALENCE • A material with MORE THAN 4 VALENCE ELECTRONS. • glass, mica, hard rubber

231

Semiconductor

S$micon"uctor

232

Energy Gap (Eg) Comparison

• A material with EXACTLY 4 VALENCE

ELECTRONS. • Semiconductors have electrical characteristics in between conductors and insulators. • SILICON, GERMANIUM are examples of semiconductor materials.

%n$r&y 'a( )%&* Com(arison

233

+on"in& of Atoms

234

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Energy Gaps • • • • • •

Silicon Germanium Silicon Carbide Aluminum Phosphide Gallium Arsenide Indium Phosphide

Bonding of Atoms

1.11 eV 0.67 eV 2.86 eV 2.45 eV 1.43 eV 1.35 eV

• Ionic Bond • Metallic Bond • Covalent Bond

235

236

#onic +on"

Ionic Bond

Metallic Bond

• Results from attractive forces between

• Results from attractive forces between a

positive and negative ions or between pairs of oppositely charged ions.

group of positive ions and a sea of electrons that are free to move about among its ions.

237

M$tallic +on"

Co,al$nt +on"in&

238

Covalent Bonding • Results when atoms

SHARE THEIR VALENCE ELECTRONS with other atoms . • The shared electrons are attracted simultaneously to two atoms resulting in a force that holds them together. Con"uction in S$micon"uctors

239

240

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Conduction in Semiconductors

Electron Flow

• Electron current flow • Hole current flow

241

%l$ctron lo.

Hole Flow

242

ol$ lo.

Types of Semiconductor Materials • Intrinsic Material • Extrinsic Materials – A Semiconductor that – Semiconductor is FREE FROM materials with SOME IMPURITIES, such as IMPURITIES ADDED to Silicon or Germanium. change its electrical properties. – The process of adding impurities is called DOPING.

y($s of S$micon"uctor mat$rials

243

y($ of %trinsic Mat$rials

Type of Extrinsic Materials

Type of Extrinsic Material

• N-TYPE

• P-TYPE

SEMICONDUCTORS

SEMICONDUCTORS

– An extrinsic

– An extrinsic

semiconductor material formed by adding DONOR impurities, such as as PENTAVALENT atoms. – Majority carriers are ELECTRONS – Minority carriers are HOLES y($ of %trinsic Mat$rial

244

semiconductor material formed by adding ACCEPTOR impurities, such as TRIVALENT atoms. – Majority carriers are HOLES – Minority carriers are ELECTRONS 245

y($s of !o($s

246

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Question

Types of Dopes • DONOR or

• ACCEPTOR or

PENTAVALENT ATOMS • N-TYPE

TRIVALENT ATOMS • P-TYPE

– PHOSPOROUS – ANTIMONY

The process of adding

– GALLIUM

• ALUMINUM • INDIUM – BORON

– ARSENIC – BISMUTH

S$micon"uctor!io"$s

impurities in a semiconductor material. a.growing b.diffusion c. doping doping d.depleting

247

The acceptor level in a doped

semiconductor

a. is near the valence band band level b.is near the conduction level c. is exactly exactly in between between the the conduction and valence band d.will depend on the concentration of doping

248

The potential required to

remove a valence electron a.valence potential b.threshold potential c. critical critical potential potential d.ionization potential

249

The movement of charge

Impurities with five

carriers in a semiconductor even without the application of electric potential. a. diffusion diffusion current current b.conventional current c. drift drift curren currentt d.saturation current

250

valence electrons. a.Acceptor b.donor c. Trivalen Trivalentt d.pentavalent 251

252

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In a semiconductor material,

An example of an

what will happen to the number of free electrons when the temperature rises?

elemental semiconductor. a.Germanium (Ge) b.Gallium Arsenide (GaAs) c. Gallium Gallium Phosphide Phosphide (GaP) d.Aluminum Arsenide (AlAs) 253

Current flow in a

semiconductor that is due to the applied electric field. a.diffusion current b.conventional current c. drift drift velocity velocity d.drift current

a. increases increases b.decreases exponentially c. decrea decreases ses d.remains the same

Which of the following is

an example of a compound semiconductor? a.Gallium Arsenide (GaAs) b.Gallium Phosphide (GaP) c. Aluminum Aluminum Arsenide Arsenide (AlAs) d.All of the above

255

If the substance used in

doping has less than four valence electrons, it is known as a. acceptor acceptor b.donor c. trival trivalen entt d.pentavalent

254

257

256

Theoretically, where does

the conduction of holes occur in a doped semiconductor? a. conduction conduction band band b.forbidden band c. valence valence band d.empty d. empty band band 258

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Typically, how how much energy

is required for a valence electron to move to the conduction band for a doped semiconductor?

The electrical resistance of a

semiconductor material will _____ as the temperature increases. a. increase increase b.increase exponentially c. decrea decrease se d.not d. not change change

a. 0 eV eV b. 0.05 eV c. 1.0 1.0 eV eV d. 5.0 eV 259

260

The PN Junction • When the P-TYPE

material and N-TYPE material are BROUGHT TOGETHER, they form a so-called PN JUNCTION.

Semiconductor Diodes

$ P unction

261

Formation of Depletion Region

Barrier Potential • The POTENTIAL

• The region created by

DIFFERENCE of the electric field across the depletion region is the AMOUNT OF VOLTAGE required to move electrons through the electric field. • 0.7V for Silicon • 0.3 for Germanium • Barrier potential DECREASES as temperature INCREASES

the PN junction forming a barrier potential. • The DEPLETION refers to the fact that the region near the PN junction is DEPLETED of CHARGED CARRIERS due to diffusion across the junction.

+arri$r Pot$ntial

262

ormation of !$(l$tion $&ion

263

+iasin& t$ !io"$

264

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Biasing the Diode

Forward Bias

• BIAS refers to the use of a dc voltage to

• Is the condition that

ALLOWS CURRENT THROUGH THE PN JUNCTION to flow when a dc voltage is applied to a PN junction

establish a certain operating condition for an electronic device. • Types: – Forward Bias – Reverse Bias

265

or.ar" +ias

$,$rs$ +ias

266

Reverse Bias • Is the condition that

ESSENTIALLY PREVENTS CURRENT through the diode when a dc voltage is applied to a PN junction. • MINORITY CARRIERS – The EXTREMELY SMALL

CURRENT THAT EXIST IN THE REVERSE BIAS condition. 267

+r$a"o.nolta&$

268

Voltage-Current Characteristic of Diode

Breakdown Voltage • The MAXIMUM VOLTAGE the junction

diode can handle when reverse biased. • Also known as PEAK REVERSE VOLTAGE (PRV) OR PEAK INVERSE VOLTAGE (PIV)

olta&$-Curr$nt Caract$ristic of !io"$

269

!io"$ %ui,al$nt Circuit

270

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Diode Equivalent Circuit

Ideal Diode Model

• Ideal Diode Model • Simplified Diode Model • Linear Diode Model

• The diode is assumed

to a ZERO THRESHOLD VOLTAGE and has NO RESISTANCE when FORWARD BIAS.

271

#"$al !io"$ Mo"$l

272

Sim(lifi$" !io"$ Mo"$l

Simplified Diode Model

Linear Diode Model • The diode has

• The diode is

THRESHOLD VOLTAGE, Vth and FORWARD RESISTANCE.

assumed to have a threshold voltage but NO RESISTANCE.

273

in$ar !io"$ Mo"$l

Diode Resistance

DC or Static Resistance • DC or Static

• DC or Static Resistance • AC or Dynamic Resistance • Average AC Resistance

!C or Static $sistanc$

274

!io"$ $sistanc$

Resistance is the FORWARD RESISTANCE of the diode when in DC circuit analysis.

275

AC or !ynamic $sistanc$

276

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AC or Dynamic Resistance

Average AC Resistance

• AC or Dynamic

• Average AC

Resistance of the diode when in AC circuit analysis.

A,$ra&$ AC $sistanc$

Resistance is the forward resistance of the diode in AC circuit analysis.

277

When a diode is reverse biased the

depletion region widens, since it is in between positively charge holes and negatively charge electrons, it will have an effect of a capacitor, this capacitance is called what? a. diffusion diffusion capacita capacitance nce b. storage storage capacit capacitance ance c. stray stray capaci capacitan tance ce d. transition transition capacita capacitance nce

%l$ct (ar r$ctifi$r !io"$s

278

In a semiconductor diode, the total

capacitance, that is the capacitance between terminals and electrodes, and the internal voltage variable capacitance of the junction is called a. diffusion diffusion capac capacitanc itance e b. transitio transition n capacita capacitance nce c. depletion depletion-regi -region on capacitanc capacitance e d. diode diode capacitanc capacitance e

279

280

In semiconductor materials,

What capacitance is

significant when the diode is forward biased? a. diffusion diffusion capacitance capacitance or storage capacitance b.transition capacitance c. depletiondepletion-region region capacitance capacitance d.stray capacitance

281

electrons have a higher value of mobility than holes, but which semiconductor material has the slowest electron-mobility? a. InSb InSb b. GaP GaP c. GaAs GaAs d. AlP AlP 282

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In the design of high power

semiconductor devices, it involves what factors?

Special-Purpose Diodes

a. making the size size of the semiconductor bigger b. packing packing the device into a bigger bigger case c. excellent excellent contact contact between between the semiconductor and the case d. all of thes these e

283

Zener Breakdown

Zener Diodes

• ZENER BREAKDOWN occurs in Zener

• Zener Diode is a s ilicon

PN junction device that differs from rectifier diodes because it is DESIGNED FOR OPERATION IN THE REVERSEBREAKDOWN REGION. • Developed by Dr. Carl Zener in 1934

diodes at low reverse voltage. • The Zener diode is heavily doped to reduce the breakdown voltage. • Types of reverse breakdown – Zener Breakdown – Avalanche Breakdown

285

$n$r +r$a"o.n

$n$r +r$a"o.n

Zener Breakdown

286

Avalanche Breakdown

• Breakdown voltage < 5V

A,alanc$ +r$a"o.n

284

$n$r !io"$s

• Breakdown voltage > 5V

287

$n$r !io"$ A((lication

288

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Zener Diode Application

Tunnel Diode • A tunnel diode is biased to operate in the

• Zener Diodes are

negative resistance region. • It can be used as an oscillator or an amplifier. • Tunnel diodes are also used extensively in highspeed switching circuits because of the speed of the tunneling action. (up to 5Ghz) • Developed by LEO ESAKI in 1958

often used as a type of of VOLTAGE REGULATOR for providing stable reference voltages.

289

unn$l !io"$

290

aractor

Varactor Voltage-Variable Capacitor is a device • Voltage-Variable that utilizes the variation of the PN junction capacitance when biased differently.

291

i&t-%mittin& !io"$ )%!*

292

Light-Emitting Diode (LED) arsenide (AlGaAs) - red and • Aluminum gallium arsenide (AlGaAs)

• A type of PN junction that emits light

infrared

when forward bias. • The large exposed surface area on one layer of the semiconductive material permits the photons to be emitted as visible light. • The process is called ELECTROLUMINESCENCE. Poto"io"$

phosphide (AlGaP) - green • Aluminum gallium phosphide (AlGaP) phosphide (AlGaInP) • Aluminum gallium indium phosphide (AlGaInP)

high-brightness orange-red, orange, yellow, and green phosphide (GaAsP) - red, • Gallium arsenide phosphide (GaAsP) orange-red, orange-red, orange, and yellow phosphide (GaP) - red, yellow and green • Gallium phosphide (GaP) nitride (GaN) - green, pure green (or • Gallium nitride (GaN) emerald emerald green), and blue also white (if it has an AlGaN Quantum Barrier) 293

294

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Photodiode nitride (InGaN) - near • Indium gallium nitride (InGaN) • • • • •

• Photodiode is a device that operates in

ultraviolet, bluish-green and blue Silicon carbide (SiC) carbide (SiC) as substrate — blue Silicon (Si) Silicon (Si) as substrate — blue (under development) Sapphire (Al2O3) Sapphire (Al2O3) as substrate — blue Zinc selenide (ZnSe) selenide (ZnSe) - blue Diamond (C) Diamond (C) - ultraviolet 295

REVERSE BIAS. • A Photodiode current increases as light strikes into its opening. • The photodiode has a small transparent window that allows light to strike the PN junction.

296

DIODE MAINTENANCE

DIODE MAINTENANCE • Diodes are rugged and efficient. • One of the greatest dangers to the diode

is heat. • THERMAL RUNAWAY – A conduction that exists when heat causes

more electron-hole pairs to b generated; which, in turn, causes more heat and may eventually cause diode destruction.

ransistors

Which semiconductor is

298

The charged-coupled device

(CCD) is a unique and versatile semiconductor structure invented in 1969 by

mostly used to detect near infrared? a.silicon b.germanium c. carbon carbon d.silicon carbide 299

a. W.S.Boyle and G.E. Smith Smith b. W.F. Davis and R. Huntington c. Cave and W. W. Blood Jr. Jr. d. H.H. Stellrecht and S. Meyer 300

50

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What semiconductor that

For an electroluminescent of

is good for hightemperature applications?

green and red lights, which semiconductor is best?

a.indium antimonide (InSb) b.gallium antimonide (GaSb) c. silicon silicon carbide carbide (SiC) d.diamond (C)

a. silicon silicon carbide carbide b.gallium arsenide c. indium antimonide antimonide d.gallium phosphide

301

Which of the following

302

The primary use of Zener

semiconductors has the smallest energy gap?

diode in electronic circuits. a.resistance regulator b.rectifier c. voltage voltage regulator regulator d.current regulator

a.ZnS b.Si c. Ge d.InSb 303

A diode that is especially

designed to operate as a voltage-variable capacitor. It utilizes the junction capacitance of a semiconductor diode. a. varac varacto torr b. varicap varicap c. varis varisto torr d. A and B are correct correct 305

304

The capacitance of a varactor

will ______ when the forward bias voltage is increase a. increase increase b.decrease c. exponentia exponentially lly decrease decrease d.not d. not change 306

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The ratio of the diode capacitance

Refers to a special type of

at a minimum reverse voltage to the diode capacitance at a maximum reverse voltage in a varactor diode.

diode which is capable of both amplification and oscillation. a. Junction Junction diode diode b.Tunnel diode c. Point Point contact contact diode diode d.Zene d. Zenerr diode

a. Tunin Tuning g ratio ratio b. Capacitan Capacitance ce ratio ratio c. Both Both a and and b d. None None of these these 307

A light emitting diode (LED) is to be

used in a circuit with a supply voltage of 5 V. What should be the value of the resistor needed by the LED to operate normally? a. 25 Ω b. 25 250 0Ω c. 25 kΩ kΩ d. 250 250 kΩ kΩ

309

308

The process of emitting

photons from a semiconductive material is called a. photoluminescence b.gallium arsenide c. electrolumi electroluminesc nescence ence d.gallium phosphide

310

Silicon and Germanium are

LED which emits infrared

not used in LEDs because ___.

radiation.

a. They emit heat instead of light b.They emit very low amount of emitted light c. They have have low thresho threshold ld voltage d.A and b are correct

a.GaAs b.GaAsP c. GaP GaP d.AlGaP 311

312

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A diode capable of

Schottky diodes are also

regulating current.

known as ___.

a.Constant-current diode b.Zener diode c. Current-controlled device d.All of these

a.Hot-carrier diode b.Tunnel diode c. PIN diode diode d.Point-contact diode 313

A diode consisting of

heavily doped p and n regions separated by an intrinsic region. a. Hot-carrier Hot-carrier diode diode b.Tunnel diode c. PIN diode diode d.Point-contact diode

314

A semiconductor diode which

employs graded doping where the doping level of the semiconductive materials is reduced as the pn junction is approached. a. Schott Schottky ky diode diode b. PIN diode diode c. Step-reco Step-recovery very diode diode d. Tunnel Tunnel diode diode

315

316

A semiconductor diode

constructed with heavily doped p and n germanium or gallium arsenide regions to have a very narrow depletion region.

Transistors

a. Schottk Schottky y diode diode b. PIN diod diode e c. Step-rec Step-recove overy ry diode d. Tunnel Tunnel diode diode 317

+i(olar unction ransistors )+*

318

53

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Transistors

Point-Contact Transistor

• The word is a contraction of TRANSfer

and resISTOR. • December 23,1947 the first transistor was demonstrated by Walter Brattain and John Bardeen.

ransistor in,$ntors :illiam Socl$y 319 )s$at$"*; on +ar"$$n;

320

Uses of BJT

Bipolar Junction Transistors (BJT) • BJT is constructed with three doped

semiconductor regions separated by two PN junctions. • BIPOLAR refers to TWO CHARGED CARRIERS: Electrons and Holes. • The Three Terminals: Emitter, Base and Collector

• Amplifier • Switch • Impedance Matching

321

y($s of +

322

Types of BJT

Transistor Operation

Reverse bias junction

Forward bias junction

ransistor <($ration

323

+iasin& an" <($rations

324

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Biasing and Operations

Characteristic Curve

325

Caract$ristic Cur,$

326

ransistor confi&uration

Transistor Configurations

Common Base

• Common Base • Common Emitter • Common Collector

327

Common +as$

Common Base

Alpha • Common Base

• Mainly used for IMPEDANCE MATCHING • Low input impedance (30Ω - 550 Ω) • High output impedance (250k Ω - 550k

Amplification Factor. • It is the ratio of the collector current change to the change in emitter current. • Ranges from 0.9 to 0.999

Ω) • ALPHA should be less than 1

Al(a

328

Al(a

329

Common %mitt$r

330

55

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Common Emitter

Common Emitter • Frequently used in practical amplifier • Provides good voltage, current and

power gain • Low input resistance (500Ω - 1500 Ω) • High output impedance (30kΩ - 50kΩ)

331

+$ta

332

Al(a

Beta

Common Collector

• Common Emitter

Forward Current Amplification Factor • It is the ratio of change in collector current to the base current. • Beta ranges from 20 to 600 333

Common Coll$ctor

334

'amma

Comparison of Transistor Configuration

Gamma • Common Collector

Forward Current Amplification Factor. • It is the ratio of change in emitter current to the base current.

Com(arison of ransistor Confi&uration

335

y($s of +iasin&

336

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Types of Biasing • • • •

Fixed Bias

Fixed-bias Emitter stabilized Voltage divider Voltage Feedback

i$" +ias

• Fixed bias has the

HIGHEST POWER GAIN but the most UNSTABLE • Base current bias

337

Emitter Stabilized

Voltage Divider Bias

• Emitter is MORE

• Voltage Divider Bias

STABLE COMPARED TO FIXED BIAS but with LESSER GAIN.

is considered the most stable but relatively lower in gain.

339

olta&$ !i,i"$r +ias

Voltage Feedback

olta&$ $$"=ac

340

Field Effect Transistors (FET)

• Almost the same

• A unipolar, voltage-controlled device

with voltage divider bias but with LESS NUMBER OF RESISTORS • SELF-BIAS

i$l" %ff$ct ransistors )%*

338

%mitt$r Sta=ili>$"

where the voltage between the two terminals, gate and source controls the current through the device.

341

y($s of f$t

342

57

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FET Characteristics

Types of FET

• Has extremely high input impedance • • • • •

• Junction FET (JFET) • Metal Oxide Semiconductor FET

(about 100M ohm) Has no offset value when used as a switch Relatively immune to radiation Less noisy Has greater thermal stability Greater susceptibility to damage.

(MOSFET) – Depletion Type – Enhancement Type

343

344

unction % )%*

Junction FET (JFET) (JFET )

Construction of JFET

terminals: • JFETs terminals: – SOURCE(S) – DRAIN(D) – GATE(G). • Two types: – N-CHANNEL – P-CHANNEL.

345

Construction of %

N-channel JFET

P-cann$l %

346

-cann$l %

P-channel JFET

347

M
348

58

6/21/2014

MOSFET

MOSFET (Depletion Type)

• Has no PN junction • Gate is insulated from the channel by

SiO2. • TYPES – Depletion – Enhancement

M
349

M
350

MOSFET (Depletion Type) Operation #OSF* (.epletion pe!

M
351

352

MOSFET (Enhancement Type) #OSF* (*nhanceent pe!

353

354

% %!

59

6/21/2014

END of Session

355

60

Amplifiers, Oscillators, Microelectronics - TIP

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