Course Outline - Weber State Universityfaculty.weber.edu/snaik/EE3110/01Chapter 1.pdf · Course Outline 1 1. Chapter 1: ... Bipolar Junction Transistors (BJT) 6. Chapter 2 ... Chapter

EE 3110 Microelectronics I Suketu Naik

1Course Outline

1. Chapter 1: Signals and Amplifiers

2. Chapter 3: Semiconductors

3. Chapter 4: Diodes

4. Chapter 5: MOS Field Effect Transistors (MOSFET)

5. Chapter 6: Bipolar Junction Transistors (BJT)

6. Chapter 2 (optional): Operational Amplifiers


2

Chapter 1:

Signals and Amplifiers


31.1 Signals

Signal, Transducer, Signal Processing


41.1 Signals

Signal – contains information

e.g. voice of radio announcer reading the news

Transducer – device which converts signalfrom non-electrical to electrical form

e.g. microphone (sound to electrical)

Process – an operation which allows an observer to understand this information from a signal

generally done electrically


5Analog Circuit Design 101

Both art and engineering

Minimize expensive components

Maximize circuit robustness

Insensitive to part selection

Insensitive to operating environment

Know that semiconductor devices

1) Are highly nonlinear

2) Are sensitive to temperature changes

3) Can vary from part to part (matching issue)


6Introduction [1/2]

Chapter Summary

Electronic circuits process signals, and thus understanding electrical signals is essential

Thevenin and Norton representations of signal sources

The representation of a signal as sum of sine waves

The analog and digital representations of a signal


7Introduction [2/2]

Chapter Summary

Most basic and pervasive signal-processing function: signal amplification, and correspondingly, the signal amplifier

Amplifiers are characterized (modeled) as circuit building blocks independent of their internal circuitry

How the frequency response of an amplifier is measured, and how it is calculated


81.1. Signals

Figure 1.1: Two alternative representations of a signal source: (a) the

Thévenin form; (b) the Norton form.


9Thevenin and Norton Equivalent Sources

Consider two source / load combinations to upper-right.

note that output resistance of a source limits its ability to deliver a signal at full strength

Q (a): what is the relationship between the source and output when maximum power is delivered?

for example, vs < vo? vs > vo? vs = vo?

Q (b): what are ideal values of RS for thevenin and norton representations?


10Time and Frequency Domain

Figure 1.5 A symmetrical

square-wave signal of

amplitude V

Figure 1.6 The frequency

spectrum (also known as

the line spectrum) of the

periodic square wave of

Fig. 1.5.

Periodic Signals Discrete Spectra


111.2 Frequency Spectrum of Signals

Frequency spectrum – defines the a time-domain signal

in terms of the strength of harmonic components

Q: What is a Fourier Series?

A: An expression of a periodic function as the sum

of an infinite number of sinusoids whose frequencies

are harmonically related


12

0

1

Fourier Series Representation of ( )

1 ( ) ( )

1 ( ) ( )

( ) ( ) (

, 0

,

)2

1

k kk

k

k

x

a x kx d

ax a kx b kx

nx

b x k nx dx

f

f cos

f cos sin

f sin

Decomposition – of a periodic function into the

(possibly infinite) sum of simpler oscillating functions

What is a Fourier Series?


131.2 Frequency Spectrum of Signals

Q: Can the Fourier Transform be applied to a non-periodic

function of time?

A: Yes, however (as opposed to a discrete frequency

spectrum) it will yield a continuous spectrum…


141.3 Analog and Digital Signals

analog signal

discrete-time signal

is continuous with respect

to both value and time

is continuous with respect to value

but sampled at discrete points in time


151.3 Analog and Digital Signals

Digital signal – is quantized (applied to values) as well as

sampled at discrete points in time


161.4 Amplifiers

Q: Why is signal amplification needed?

A: Because many transducers yield output at low power

levels (mW or nW)

Linearity – is property of an amplifier which ensures a

signal is not “altered” from amplification

Distortion – is any unintended change in output


171.4.1 Signal Amplification

Voltage amplifier – is used to boost voltage levels for

increased resolution.

Power amplifier – is used to boost current levels for

increased “intensity”.

output / input relationship for amplifier

( ) ( )o v it A tv v

voltage gain


181.4.4 Power and Current Gain

Q: What is one main difference between an amplifier

and transformer? (both alter voltage levels)

A: Amplifier may be used to boost power delivery

( ) ( )

( )L o o

p

I i i

load power P v ipower gain A

input power P v i


191.4.6 Amplifier Power Supply

Figure 1.13: An amplifier that requires two dc supplies (shown as

batteries) for operation.


201.4.7 Amplifier Saturation

Limited linear range – practically, amplifier operation

is linear over a limited input range

Saturation – beyond this input range, saturation

occurs.

output remains constant as input varies

harmonic distortion occurs

power supply limitation


211.4.7 Amplifier Saturation

or...minus o plus

plusminusi

v v

L v L

LLv

A A


221.5 Circuit Models for Amplifiers

Model – is the description of component's (e.g. amplifier)

terminal behavior

neglecting internal operation / transistor design

values of the model parameters are found by

measurements and analysis


231.5.1 Voltage Amplifiers

model of amplifier input terminals

sourcevolt.

source andinput

resistances

input vo tag )l e ( ii s

i s

Rv v

R R

model of amplifier output terminals

open-cktoutput

output andvoltageload

resistances

output vo (l )tage Lo vo i

L o

Rv A v

R R

Figure 1.16 (b): voltage amplifier with input signal source



Q: What is the “problem” with this model?

A: Gain (ratio of vo and vs) is not constant, and

dependent on input and load resistance.

sourcevolt.

source and output andinput load

resistances resistances

open-ckt output voltage

( ) i L i Lo vo s vo s

i s L o i s L o

R R R Rv A v A v

R R R R R R R R

The ideal amplifier model neglects this nonlinearity.



Ideal amplifier model – is function of vs and Avo only!!

It is assumed that Ro << RL…

It is assumed that Ri >> Rs…

idealmodel

non-ideal model

i Lo vo s vo s

i s L o

R Rv A v A v

R R R R

Key characteristics of ideal voltage amplifier model

1) Source resistance RS and load resistance RL have no effect on gain

2) High input resistance Ri (>>RS) and low output resistance Ro(<<RL)


26Example 1.3: Cascaded Amplifier Configurations

Figure 1.17: Three-stage amplifier for Example 1.3.

• High Input Resistance

• Modest Gain

• Low Input Resistance

• High Gain

• Low Output Resistance

• Unity Gain


27Example 1.3: Cascaded Amplifier Configurations

Figure 1.17: Three-stage amplifier for Example 1.3.

aggregate amplifier with gain

Lv

s i s

vA

v i R


281.5.3 Amplifier Types

voltage amplifier current amplifier

0

00

0

with 0

i

v

oi i

RvA

Rv

0

00

0

0 with

i

v

oi v

RiA

Ri

open circuit voltage gain short circuit current gain


291.5.3 Amplifier Types

transconductance amp. transresistance amp.

0

0

0

with i

m

oi v

RiG

Rv

0

0

0

0 with

0i

m

oi i

RvR

Ri

short circuit

transconductance

open circuit

transresistance


301.5.4 Relationship Between Four Amp Models

Interchangeability – although these four types exist,

any of the four may be used to model any amplifier

they are related through Avo (open circuit gain)

currenttransres.to voltage

to voltagetranscond.amplifieramplifierto voltage

amplifier

o mvo is m o

i i

R RA A G R

R R

30


311.5.5 Determining Ri and Ro

Q: How can one calculate input resistance from terminal behavior?

A: Observe vi and ii, calculate via Ri = vi / ii

Q: How can one calculate output resistance from terminal behavior?

A:

Remove source voltage (such that vi = ii = 0)

Apply voltage to output (vx)

Measure negative output current (-io) or current going into the output terminal as ix

Calculate via Ro = -vx / io = vx / ix

31


321.6.1 Amplifier Frequency Response

input and output are similar for linear amplifier

same frequency

different amplitude and phase

32


331.6.1 Amplifier Frequency Response

Amplifier transfer function (T) – describes the

input-output relationship of an amplifier – or other

device – with respect to various parameters, including

frequency of input applied.

It is a complex value, often defined in terms of

magnitude and phase shift.

phase shift

magnitude gain

( ) )and ( o

i

V

V T T


341.6.2 Amplifier Bandwidth

Q: What is bandwidth of a device?

A: The range of frequencies over which its magnitude

response is constant (within 3dB).

Q: For an amplifier, what is main bandwidth concern?

A: That the bandwidth extends beyond range of

frequencies it is expected to amplify.


351.6.4 Single Time-Constant Networks

Figure 1.22: Two examples of STC networks: (a) a low-pass

network and (b) a high-pass network.

Amplifier's frequecy response can be categorized as low or high

pass filters


36

Figure: Low-Pass Filter Magnitude (top-left) and Phase (top-right) Responses as well as High-Pass Filter (bottom-

left) and Phase (bottom-right) Responses

Frequency Response


371.6.4. Single Time-Constant Networks

0 0

0 0

2 20 0

Characteristics of Various STC

1 ( / ) 1

1 ( / ) 1 ( / )

1 ( / ) 1 ( / )

K Ks

s

K K

j j

K K

j j

Figure 1.2 :

low - pass high - pass

transfer function

transfer function

(for physical freq.)

magnitude response

phase respon 0 0

0

( / ) ( / )

0 0

0

13 same

refer to next slide

K

K

db

se tan tan

transmission at

transmission at

Frequency

Bode Plots

τ = CR

(or L/R)


38Example 1.5: Voltage Amplifier

Examine voltage amplifier with:

input resistance (Ri), input capacitance (Ci), gain factor (m), output resistance (Ro)

(a): Derive an expression for the amplifier voltage gain

Vo / Vs as a function of frequency. From this, find expressions for the dc gain and 3dB frequency.


391.6.5 Classification of Amps Based on Frequency Response

Internal capacitances – cause the falloff of gain at high

frequencies (previous example)

Coupling capacitors – cause the falloff of gain at low

frequencies

are placed in between amplifier stages

generally chosen to be large

Documents

Course Outline - Weber State Universityfaculty.weber.edu/snaik/EE3110/01Chapter 1.pdf · Course Outline 1 1. Chapter 1: ... Bipolar Junction Transistors (BJT) 6. Chapter 2 ... Chapter