Analog Electronics Introduction

8/17/2019 Analog Electronics Introduction

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Analog Electronics

Section 1

Prof. Dr. Murat Aşkar D-211

E-mail: [email protected]

Web: www.eee.metu.edu.tr/~askar


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Analog and Digital Signals


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Analog Signals are links to the real world


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Transreceiver


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Bio-eng: Neuronal implants


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Linear Amplifiers (1)

Multiply amplitude of a signal by a constant scalar quantity

xo(t) = A xi(t)

Non-scalar or

non-uniformamplification

is called

distortion


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Linear Amplifiers (2)

• Symbol for a single-ended

input linear voltage amplifier.

• Ideally provides linear

voltage gain regardless of

the amplitude of the input

signal

• Real amplifiers have power

supplies that limit theamplitude of the output

• If input is too large, output

clamps


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Transfer Characteristics (1)

Plot of amplifier output versus amplifier input


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Transfer Characteristics (2)

• Gain = Slope

• To operate amplifier in its linear region, the input

must be kept small enough


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Real Transfer Characteristics

• Each circle represents

a different DC

component for the

input and output

signals – called an

operating point

• Location of operating

point has an effect on

• input signal range

• amplifier gain magnitude

• amount of distortion


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Operating Point (1)

Voltage gain, output DC voltage, allowable input

magnitude range are affected


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Operating Point (2)

Derivative of

transfer

characteristicgives measure

of amplifier gain

linearity (and

distortion)

Input and output signal amplitude ranges are

maximized when operating point is near middle of

linear region


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Signal Convention (1)

• DC magnitudes in uppercase symbol and

subscript

– Example: ID, VD

• Ac signal quantities in lowercase symbol &

subscript

– Example: id(t), vd(t)

• Total DC + ac signal quantities in lowercase

symbol, uppercase subscript – Example: iD(t), vD (t)


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Signal Convention (2)In general

vD(t) = VD + vd(t)

iC(t) = IC + ic(t)


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Superposition

• If the amplifier is linear, superposition can be

applied. Each component can be determined

seperately.• Determine the DC magnitude of the output using

DC model , i.e capacitors are open circuited,

inductors are short circuited. ( Example: IY, VX)• Determine the ac signal component of the output

using the ac model , i.e., DC sources are killed

and capacitors are short circuited, inductors are

open circuited. (Example: vy(t) = Av vi(t))

• Total output is then: vY(t) = V

Y + v

y(t)


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Amplifier Classification

CurrentCurrentCurrent

TransresistanceVoltageCurrent

TransconductanceCurrentVoltage

VoltageVoltageVoltage

TypeOutputInput


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+

vi-

+

vo-

Ideal Voltage Amplifier

Avi

+

R oAvi

+

vi-

+

vo-

R i

+

Real Voltage Amplifier


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Loaded Ideal Voltage Amplifier

Avi

+

vi-

+

vo-

+

R LR s

vs

+

Av

v

s

o=


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Loaded Voltage Amplifier

R oAvi

+

vi-

+

vo-

R i

+

R LR s

vs

+

Lo

L

is

i

s

o

R R

R

R R

R A

v

v

++=


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Ideal Current Amplifier

Real Current Amplifier

Aii

ii io

Aiiii ioR i R o


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Loaded Ideal Current Amplifier

Ai

i

s

o=

Aii R L

ii

R sis

io


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Loaded Current Amplifier

Aii R L

ii

R Sis

io

R i R o

Lo

o

is

s

s

o

R R

R

R R

R A

i

i

++=


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To determine Input Resistance R i

R oAvi

+

vi-

+

vo-

R i

+

• Apply input voltage vi

(or input current ii)• Determine the input

current ii (or input

voltage vi)Then

R i

= vi

/ iiAii

ii io

R i R o

ii

+

vi-

Voltage Amplifier

Current Amplifier


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To determine Output Resistance R o

R oAvi

+

vi-

+

vx-

R i

+

• Kill the input signal

(set vi or ii to zero)• Apply a test voltage

vx to the output node

• Determine the currentix that the source

delivers to the circuit

Then

R o = vx / ix

Aii

ii ix

R i R o

ii

+

vi-

Voltage Amplifier

Current Amplifier

+

vx-

ix

Documents

Analog Electronics Introduction