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BR Wiley/Razavi/Fundamentals of Microelectronics [Razavi.cls v. 2006] June 30, 2007 at 13:42 1 (1)
1
Introduction to Microelectronics
Over the past five decades, microelectronics has revolutionized our lives. While beyond the realm
of possibility a few decades ago, cellphones, digital cameras, laptop computers, and many other
electronic products have now become an integral part of our daily affairs.
Learning microelectronics can be fun. As we learn how each device operates, how devices
comprise circuits that perform interesting and useful functions, and how circuits form sophisti-
cated systems, we begin to see the beauty of microelectronics and appreciate the reasons for its
explosive growth.
This chapter gives an overview of microelectronics so as to provide a context for the material
presented in this book. We introduce examples of microelectronic systems and identify important
circuit “functions” that they employ. We also provide a review of basic circuit theory to refresh
the reader’s memory.
1.1 Electronics versus Microelectronics
The general area of electronics began about a century ago and proved instrumental in the radio
and radar communications used during the two world wars. Early systems incorporated “vacuum
tubes,” amplifying devices that operated with the flow of electrons between plates in a vacuum
chamber. However, the finite lifetime and the large size of vacuum tubes motivated researchers
to seek an electronic device with better properties.
The first transistor was invented in the 1940s and rapidly displaced vacuum tubes. It exhibited
a very long (in principle, infinite) lifetime and occupied a much smaller volume (e.g., less than 1
cm3 in packaged form) than vacuum tubes did.
But it was not until 1960s that the field of microelectronics, i.e., the science of integrating
many transistors on one chip, began. Early “integrated circuits” (ICs) contained only a handful
of devices, but advances in the technology soon made it possible to dramatically increase the
complexity of “microchips.”
Example 1.1
Today’s microprocessors contain about 100 million transistors in a chip area of approximately
3 cm 3 cm. (The chip is a few hundred microns thick.) Suppose integrated circuits were not
invented and we attempted to build a processor using 100 million “discrete” transistors. If each
device occupies a volume of 3 mm 3 mm 3 mm, determine the minimum volume for the
processor. What other issues would arise in such an implementation?
Solution
The minimum volume is given by 27 mm3 108 , i.e., a cube 1.4 m on each side! Of course, the
1
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2 Chap. 1 Introduction to Microelectronics
wires connecting the transistors would increase the volume substantially.
In addition to occupying a large volume, this discrete processor would be extremely slow; the
signals would need to travel on wires as long as 1.4 m! Furthermore, if each discrete transistor
costs 1 cent and weighs 1 g, each processor unit would be priced at one million dollars and weigh
100 tons!
Exercise
How much power would such a system consume if each transistor dissipates 10 W?
This book deals with mostly microelectronics while providing sufficient foundation for gen-
eral (perhaps discrete) electronic systems as well.
1.2 Examples of Electronic Systems
At this point, we introduce two examples of microelectronic systems and identify some of the
important building blocks that we should study in basic electronics.
1.2.1 Cellular Telephone
Cellular telephones were developed in the 1980s and rapidly became popular in the 1990s. To-
day’s cellphones contain a great deal of sophisticated analog and digital electronics that lie well
beyond the scope of this book. But our objective here is to see how the concepts described in this
book prove relevant to the operation of a cellphone.
Suppose you are speaking with a friend on your cellphone. Your voice is converted to an elec-
tric signal by a microphone and, after some processing, transmitted by the antenna. The signal
produced by your antenna is picked up by the your friend’s receiver and, after some processing,
applied to the speaker [Fig. 1.1(a)]. What goes on in these black boxes? Why are they needed?
Transmitter (TX) Receiver (RX)
Microphone Speaker
? ?
(a) (b)
Figure 1.1 (a) Simplified view of a cellphone, (b) further simplification of transmit and receive paths.
Let us attempt to omit the black boxes and construct the simple system shown in Fig. 1.1(b).
How well does this system work? We make two observations. First, our voice contains frequen-
cies from 20 Hz to 20 kHz (called the “voice band”). Second, for an antenna to operate efficiently,
i.e., to convert most of the electrical signal to electromagnetic radiation, its dimension must be a
significant fraction (e.g., 25%) of the wavelength. Unfortunately, a frequency range of 20 Hz to
20 kHz translates to a wavelength1 of 1:5 107 m to 1:5 104 m, requiring gigantic antennas
for each cellphone. Conversely, to obtain a reasonable antenna length, e.g., 5 cm, the wavelength
must be around 20 cm and the frequency around 1.5 GHz.
1 Recall that the wavelength is equal to the (light) velocity divided by the frequency.
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Sec. 1.2 Examples of Electronic Systems 3
How do we “convert” the voice band to a gigahertz center frequency? One possible approach is
to multiply the voice signal, x(t), by a sinusoid, A cos(2fc t) [Fig. 1.2(a)]. Since multiplication
in the time domain corresponds to convolution in the frequency domain, and since the spectrum
Output Waveform
x (t ) A cos( 2 π f C t )
Voice
Signal
t t t
(a)
Spectrum of Cosine Output Spectrum
X (f )
Voice
Spectrum
−fC
+20 kHz
−20 kHz
0 f −fC 0 +fC f 0 +fC f
(b)
Figure 1.2 (a) Multiplication of a voice signal by a sinusoid, (b) equivalent operation in the frequency
domain.
of the sinusoid consists of two impulses at fc , the voice spectrum is simply shifted (translated)
to fc [Fig. 1.2(b)]. Thus, if fc = 1 GHz, the output occupies a bandwidth of 40 kHz centered
at 1 GHz. This operation is an example of “amplitude modulation.”2
We therefore postulate that the black box in the transmitter of Fig. 1.1(a) contains a
multiplier,3 as depicted in Fig. 1.3(a). But two other issues arise. First, the cellphone must deliver
Power
Amplifier
A cos( 2 π f C t ) Oscillator
(a) (b)
Figure 1.3 (a) Simple transmitter, (b) more complete transmitter.
a relatively large voltage swing (e.g., 20 Vpp ) to the antenna so that the radiated power can reach
across distances of several kilometers, thereby requiring a “power amplifier” between the mul-
tiplier and the antenna. Second, the sinusoid, A cos 2fc t, must be produced by an “oscillator.”
We thus arrive at the transmitter architecture shown in Fig. 1.3(b).
Let us now turn our attention to the receive path of the cellphone, beginning with the sim-
ple realization illustrated in Fig. 1.1(b). Unfortunately, This topology fails to operate with the
principle of modulation: if the signal received by the antenna resides around a gigahertz center
frequency, the audio speaker cannot produce meaningful information. In other words, a means of
2 Cellphones in fact use other types of modulation to translate the voice band to higher frequencies.
3 Also called a “mixer” in high-frequency electronics.
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BR Wiley/Razavi/Fundamentals of Microelectronics [Razavi.cls v. 2006] June 30, 2007 at 13:42 1 (1)
1
Introduction to Microelectronics
Over the past five decades, microelectronics has revolutionized our lives. While beyond the realm
of possibility a few decades ago, cellphones, digital cameras, laptop computers, and many other
electronic products have now become an integral part of our daily affairs.
Learning microelectronics can be fun. As we learn how each device operates, how devices
comprise circuits that perform interesting and useful functions, and how circuits form sophisti-
cated systems, we begin to see the beauty of microelectronics and appreciate the reasons for its
explosive growth.
This chapter gives an overview of microelectronics so as to provide a context for the material
presented in this book. We introduce examples of microelectronic systems and identify important
circuit “functions” that they employ. We also provide a review of basic circuit theory to refresh
the reader’s memory.
1.1 Electronics versus Microelectronics
The general area of electronics began about a century ago and proved instrumental in the radio
and radar communications used during the two world wars. Early systems incorporated “vacuum
tubes,” amplifying devices that operated with the flow of electrons between plates in a vacuum
chamber. However, the finite lifetime and the large size of vacuum tubes motivated researchers
to seek an electronic device with better properties.
The first transistor was invented in the 1940s and rapidly displaced vacuum tubes. It exhibited
a very long (in principle, infinite) lifetime and occupied a much smaller volume (e.g., less than 1
cm3 in packaged form) than vacuum tubes did.
But it was not until 1960s that the field of microelectronics, i.e., the science of integrating
many transistors on one chip, began. Early “integrated circuits” (ICs) contained only a handful
of devices, but advances in the technology soon made it possible to dramatically increase the
complexity of “microchips.”
Example 1.1
Today’s microprocessors contain about 100 million transistors in a chip area of approximately
3 cm 3 cm. (The chip is a few hundred microns thick.) Suppose integrated circuits were not
invented and we attempted to build a processor using 100 million “discrete” transistors. If each
device occupies a volume of 3 mm 3 mm 3 mm, determine the minimum volume for the
processor. What other issues would arise in such an implementation?
Solution
The minimum volume is given by 27 mm3 108 , i.e., a cube 1.4 m on each side! Of course, the
1
Save time with the right summary on
,dmuwodmfdmuwodmfdmuwodmf-580ce97c829f36c4ade0f9ec526980b4
BR Wiley/Razavi/Fundamentals of Microelectronics [Razavi.cls v. 2006] June 30, 2007 at 13:42 2 (1)
2 Chap. 1 Introduction to Microelectronics
wires connecting the transistors would increase the volume substantially.
In addition to occupying a large volume, this discrete processor would be extremely slow; the
signals would need to travel on wires as long as 1.4 m! Furthermore, if each discrete transistor
costs 1 cent and weighs 1 g, each processor unit would be priced at one million dollars and weigh
100 tons!
Exercise
How much power would such a system consume if each transistor dissipates 10 W?
This book deals with mostly microelectronics while providing sufficient foundation for gen-
eral (perhaps discrete) electronic systems as well.
1.2 Examples of Electronic Systems
At this point, we introduce two examples of microelectronic systems and identify some of the
important building blocks that we should study in basic electronics.
1.2.1 Cellular Telephone
Cellular telephones were developed in the 1980s and rapidly became popular in the 1990s. To-
day’s cellphones contain a great deal of sophisticated analog and digital electronics that lie well
beyond the scope of this book. But our objective here is to see how the concepts described in this
book prove relevant to the operation of a cellphone.
Suppose you are speaking with a friend on your cellphone. Your voice is converted to an elec-
tric signal by a microphone and, after some processing, transmitted by the antenna. The signal
produced by your antenna is picked up by the your friend’s receiver and, after some processing,
applied to the speaker [Fig. 1.1(a)]. What goes on in these black boxes? Why are they needed?
Transmitter (TX) Receiver (RX)
Microphone Speaker
? ?
(a) (b)
Figure 1.1 (a) Simplified view of a cellphone, (b) further simplification of transmit and receive paths.
Let us attempt to omit the black boxes and construct the simple system shown in Fig. 1.1(b).
How well does this system work? We make two observations. First, our voice contains frequen-
cies from 20 Hz to 20 kHz (called the “voice band”). Second, for an antenna to operate efficiently,
i.e., to convert most of the electrical signal to electromagnetic radiation, its dimension must be a
significant fraction (e.g., 25%) of the wavelength. Unfortunately, a frequency range of 20 Hz to
20 kHz translates to a wavelength1 of 1:5 107 m to 1:5 104 m, requiring gigantic antennas
for each cellphone. Conversely, to obtain a reasonable antenna length, e.g., 5 cm, the wavelength
must be around 20 cm and the frequency around 1.5 GHz.
1 Recall that the wavelength is equal to the (light) velocity divided by the frequency.
Discuss this document with others on
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BR Wiley/Razavi/Fundamentals of Microelectronics [Razavi.cls v. 2006] June 30, 2007 at 13:42 3 (1)
Sec. 1.2 Examples of Electronic Systems 3
How do we “convert” the voice band to a gigahertz center frequency? One possible approach is
to multiply the voice signal, x(t), by a sinusoid, A cos(2fc t) [Fig. 1.2(a)]. Since multiplication
in the time domain corresponds to convolution in the frequency domain, and since the spectrum
Output Waveform
x (t ) A cos( 2 π f C t )
Voice
Signal
t t t
(a)
Spectrum of Cosine Output Spectrum
X (f )
Voice
Spectrum
−fC
+20 kHz
−20 kHz
0 f −fC 0 +fC f 0 +fC f
(b)
Figure 1.2 (a) Multiplication of a voice signal by a sinusoid, (b) equivalent operation in the frequency
domain.
of the sinusoid consists of two impulses at fc , the voice spectrum is simply shifted (translated)
to fc [Fig. 1.2(b)]. Thus, if fc = 1 GHz, the output occupies a bandwidth of 40 kHz centered
at 1 GHz. This operation is an example of “amplitude modulation.”2
We therefore postulate that the black box in the transmitter of Fig. 1.1(a) contains a
multiplier,3 as depicted in Fig. 1.3(a). But two other issues arise. First, the cellphone must deliver
Power
Amplifier
A cos( 2 π f C t ) Oscillator
(a) (b)
Figure 1.3 (a) Simple transmitter, (b) more complete transmitter.
a relatively large voltage swing (e.g., 20 Vpp ) to the antenna so that the radiated power can reach
across distances of several kilometers, thereby requiring a “power amplifier” between the mul-
tiplier and the antenna. Second, the sinusoid, A cos 2fc t, must be produced by an “oscillator.”
We thus arrive at the transmitter architecture shown in Fig. 1.3(b).
Let us now turn our attention to the receive path of the cellphone, beginning with the sim-
ple realization illustrated in Fig. 1.1(b). Unfortunately, This topology fails to operate with the
principle of modulation: if the signal received by the antenna resides around a gigahertz center
frequency, the audio speaker cannot produce meaningful information. In other words, a means of
2 Cellphones in fact use other types of modulation to translate the voice band to higher frequencies.
3 Also called a “mixer” in high-frequency electronics.
Quiz yourself with flashcards on
