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Just Before Start

Analog CommunicationSem V EXTC

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Evaluation System

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Chapters

1. Basics of Communication System

2. Amplitude Modulation & Demodulation

3. Angle Modulation & Demodulation

4. Radio Receivers

5. Sampling Techniques

6. Pulse Modulation and Demodulation

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Analog CommunicationBy

Vaqar Ansari

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Electronics and

Telecommunication

Engineering

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What is a circuit?

Combination of electronic parts, wires connectedbetween power sources.

It's like a physical program.

It's also like setting up dominoes in sequence.

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What is a breadboard?

What are they good for?

Creatings, organizing, and prototyping a circuit.

Literally started out as a bread board with nails.

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What are LEDs?

Light Emitting DiodesDiode Symbol + Arrows for lightPoints to ground

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Diodes A semiconductor diode isformed with pieces of N and

P-type material are joined. The P material is called the

anode.

The N material is called thecathode.

The resulting structure is called

a PN junction.

A PN junction (or diode) is aswitch or component throughwhich electrons will flow

easily in one direction but notin the opposite direction.

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0.3(Ge) 0.7(Si)

(Ge)(Si)

VD(V)

ID(mA)

Comparison of Si and Ge semiconductor diodes

Is(Si)=10nA

Is=reverse saturation current

Is(Ge)

1

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Transistor Operation The basic operation will be described using the pnp transistor.

The operation of the pnp transistor is exactly the same if the

roles played by the electron and hole are interchanged.

One p-n junction of a transistor is reverse-biased, whereas theother is forward-biased.

Forward-biased junctionof a pnp transistor

Reverse-biased junctionof a pnp transistor

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Junction FETs

(JFETs)

JFETs consists of a piece ofhigh-resistivity semiconductormaterial (usually Si) whichconstitutes a channelfor the

majority carrier flow.

Conducting semiconductorchannel between two ohmiccontacts source & drain

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Classification scheme for

Field Effect Transistors.

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General R-L-C AC circuit

AC

R

AC

LC

Volt and current relations

tVV o cos

tVtVtVtV cRLo cos

c

tq

Vc

dt

tdq

RVR

dt

tdI

LVL

2

2

dt

tqd

L

tV

c

tq

dt

tdqR

dt

tqdL o cos2

2

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t

Z

V

dt

tdqtI o cos,

tZVtq o sin

22 Lc XXRZ 2

2 1

L

C

R

R

XX LctanR

LC

1

tIocos

XC- X

L

R

Solution of the differential equation

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-20

-10

0

10

20

30

40

50

60

0 5000 10000 15000 20000

(rad/sec)

OhmorOhm^

Xc=1/wC

XL=wL

Xc-XL

(Xc-XL)^2

R^2+(Xc-XL)^2

Z=sqrt(R^2+(Xc-XL)^2)

C =10 FL = 1mH

R = 5 ohm

LC

1Capacitive circuit Inductive circuitLC

1

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-90

-75

-60

-45

-30

-15

0

15

30

45

60

75

90

0 5000 10000 15000 20000

(rad/sec)

degr

ees

C =10 FL = 1mH

R = 5 ohm

Capacitive circuit

Inductive circuit

R

XXLc

tanR

LC

1

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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 5000 10000 15000 20000

(rad/sec)

I

o

Amp C =10 F

L = 1mHR = 5 ohm

Vo = 5 Volt

Capacitive circuit

Inductive circuit

Z

VI oo

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-1

0

1

2

3

4

5

0 0.0005 0.001 0.0015 0.002

Time (sec)

P(t)(W

att)

w=5000 rad/sec w=10000 rad/sec w=15000 rad/sec

C =10 FL = 1mH

R = 5 ohm

Vo = 5 Volt

Capacitive case, 0 Inductive case, 0Resistive case, 0

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0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

2.25

2.5

0 5000 10000 15000 20000

(rad/sec)

PavW

C =10 F

L = 1mHR = 5 ohm

Vo = 5 Volt

Capacitive circuit

Inductive circuit

RI

P oav2

2

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Root MeanSquare

2

orms

II

rmsR RIVrms

2rmsav RIP

rmsCX

IXV Crms

rmsLX IXV L

rms

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Resonance

At resonance, the capacitive reactance is equalto the inductive reactance.

LC XX LC

1

LCres

1

22 Lc XXRZ RZ res

R

XX Lctan 0res

The impedanceis minimum, and it is totally resistive.

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Resonance

-20

-10

0

10

20

30

40

50

60

0 5000 10000 15000 20000

(rad/sec)

Ohmor

Ohm^

Xc=1/wC

XL=wL

Xc-XL

(Xc-XL)^2

R^2+(Xc-XL)^2

Z=sqrt(R^2+(Xc-XL)^2)

C =10 FL = 1mH

R = 5 ohm

Z=R=5 ohm

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Resonance

-90

-75

-60

-45

-30

-15

0

15

30

45

60

75

90

0 5000 10000 15000 20000

(rad/sec)

degr

ees

C =10 FL = 1mH

R = 5 ohm

Capacitive circuit

Inductive circuit

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Resonance

At resonance, the capacitive reactance is equalto the inductive reactance, thus

The impedance is minimum.

The current is maximum.

tR

VtI res

ores cos,

t

Z

VtI o cos,

tVV resores cos

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Resonance

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 5000 10000 15000 20000

(rad/sec)

I

o

Amp C =10 F

L = 1mH

R = 5 ohm

Vo = 5 Volt

Capacitive circuit

Inductive circuit

Io=Vo/R =5/5 = 1 Amp.

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Resonance

0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

2.25

2.5

0 5000 10000 15000 20000

(rad/sec)

PavW

C =10 FL = 1mH

R = 5 ohm

Vo = 5 Volt

Capacitive circuit

Inductive circuit

Pav=V2

o/2R =25/(2*5) = 2.5 W

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Ideal Op-Amp Characteristics

Open Loop Voltage Gain (Avol) is

infinite

Input offset Voltage is zero

Input bias current is zero

No power supply limits Input impedance is infinite

Simple model is a voltage

controlled voltage source with

high gain.

Avol= -

+-

+Vosi = 0V

Vout

IB-= 0

IB+= 0

Avol= ZIN=

-

+-

+

Vout

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Close Loop GainVpos Vneg Avol Vout= (1) Input x gain = output

(2) Voltage divider equation

(remember Ib =0)Vneg Vout

R1

R1 Rf

=

Vpos Vout

R1

R1 Rf

Avol Vout= (3) Substitute 2 into 1

Vout

AvolVpos

AvolR1

R1 Rf 1

=

(4) Rearange 3

Vout

Vpos

1

R1

R1 Rf

1

Avol

=(5) Multiply num and

denom with 1/Avol

(6) Take the limit

for high gainAvol

1

R1

R1 Rf

1

Avol

lim

1

R1

R1 Rf

0

=

Rf

R1

1=

Vpos

Vneg

Avol-

+-

+

Vout

Rf 1kR1 1k

IB = 0

Vpos-

+

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Rin 1k

RF 2k

Vin

2V

Vout

0VVirtual

Short to

GND

+ 2V -

+

-

Iin= 2V/1kIin= 2mA

Simple Analysis for Inverting Amp

Rin 1k

RF 2k

Vin

2V

Vout

+

-

Iin= 2mA

2mA

VRF= 2mA x 2k = 4V

+ 4V -

Vout = -4V

With respect to GND

Gain = Vout / Vin

Gain = (-4V) / (2V) = -2

IB= 0A

Vin across Rin

Iin flows through Rf

Vout is the voltage across Rf

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R1 1k

Rf 99k

+ Vout-

+

Vin

+

Vout-

+

Vin

R1 1k

Rf 99k

+

Vout-

+

VinBuffer

Vout = Vin

Common Amplifiers

Noninverting Amp

Vout

Vin

Rf

R1

1=

Inverting Amp

Vout

Vin

Rf

R1

=

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Superposition principle

Used for circuits with multiple input sources.

Analyze the output response for one sourceat a time.

Short unused voltage sources

Open unused current sources

Repeat the analysis for each source

Add all the response from each analysis toget the overall system respones

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VrefVref

+5VR1 1k

R2 1k

+

VM1+

VG1

+

-

U1 OPA333

V

Vref

Vref

+5VR1 1k

R2 1k

+

VM1

+

-

U1 OPA333

V

Vref

VrefVref

+5VR1 1k

R2 1k

+

VM1+

VG1

0.1V

+

-

U1 OPA333

V

-1 x Vref = -Vref

W.R.T.G

2(Vg1 + Vref)

W.R.T.G

(2Vg1 + 2Vref) + (-Vref)=2Vg1 +Vref W.R.T. GND

(2Vg1 +Vref)Vref =2Vg1 W.R.T. Ref

2Vg1

w.r.t Ref

2Vg1 +Vref

w.r.t.g

Superposition Example: Single Supply Amp

(Noninverting)

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R3 40k

R4 40k

R5 40k

R6 40k

Vout

Va1

Va2

-

+

A3

Output Stage

Dif Amp

R3 40k R5 40k

Vout

Va1

-

+

A3

R3 40k

R4 40k

R5 40k

R6 40k

Vout

Va2

-

+

A3

Va1

Va2

Va2+ Vref

Find Vout Through Superposition

Vout = Va2Va1+ Vref

Inverting Amp

Gain = -1

Non-inverting Amp

Gain = 2

Voltage Divider

Gain = 1/2

Va1

Vin_dif

Va2

-Va1

Vref

Va22

+Vref2

Vref

Superposition Example : Diff Amp

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Cf Filter (High Gain)

At high frequency CF will short

RF

High Freq Gain = 0/1k+1 = 1

At low frequency CF acts like

an open

DC Gain = (99k/1k)+1 = 100

-15V

+15V

R1 1k

Rf 99k

+

Vout

Cf 10n

-

+

U1 OPA827

Vin

fp1

2 99 k10 nF160.8Hz

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Gain(dB)

-10.00

0.00

10.00

20.00

30.00

40.00

Frequency (Hz)

1.00 10.00 100.00 1.00k 10.00k 100.00k 1.00M

Phase[deg]

-80.00

-60.00

-40.00

-20.00

0.00

fp1

2 99 k10 nF160.8Hz

High Frequency

Gain = 1 (0dB)

Low Frequency

Gain = 100 (40dB)

-45o/ decade

+45o/ decade

Zero at f= 16.08kHz

40dB / 20dB/dec = 2 decades.

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Cf Filter (Low Gain)

At high frequency CF will

short RF

High Freq Gain = 0/1k+1 = 1

At low frequency CF acts like

an open

DC Gain = (2k/1k)+1 = 3

-15V

+15VR1 1k

Rf 2k

+

Vin

Vout

Cf 10n

-

+

fp1

2 2 k10 nF8 10

3 Hz

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Gain(dB)

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

Frequency (Hz)

1.00 10.00 100.00 1.00k 10.00k 100.00k 1.00M

Phase

[deg]

-40.00

-30.00

-20.00

-10.00

0.00

High Frequency

Gain = 1 (0dB)

Low Frequency

Gain = 3

(9.54dB)

-45o/decade +45o/

decade

Zero

fp1

2 2 k10 nF8 10

3 Hz

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Analog

Discrete

Digital

Signals

Periodicity

Periodic

Non periodic

Nature ofsample

Random

Deterministic

Odd/Even

EnergySignal

Power Signal

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System

Linearity

Causality

StabilityTime

Invariant/Variant

Static/Dynamic

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FT

Spectrum

ParsivalsRelationship

DFT & FFT

LT

Initial Value Theorem

Final Value Theorem

ZT Pole & Zeros on ROC Residue Theorem

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Just Start