Lecture 7. The Microchip
Informal and unedited notes, not for distribution. (c) Z. Stachniak, 2011.
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Looking inside our desktop computers, laptops, and smartphones, following
wires inside our cars, elevators, fridges, wrists watches, radios and audio
equipment, searching through circuitry controlling ”smart” trains, airplanes,
spacecraft, process control and test equipment, taking oﬀ covers of electronic
equipment, we don’t see vacuum tubes any more. Instead, we see electronic
boards populated with all sorts of tiny devices. Some of them are rectangu-
larly shaped black blocks of plastic with numerous metal leads extending out
of them and into the board. We call them integrated circuits.
Fig. 1. A smart phone’s circuit board with integrated circuits. Source: unknown.
In fact, what we see are not ”circuits” themselves as they are packaged in
plastic or ceramic, mostly non-transparent enclosures.
1 Integrated circuits are small and use little energy; but they can implement
electronic circuits of immense complexities. That’s why large calculators
could be turned into pocket-sized gadgets and large mainframe computers
into small servers, desktops, and laptops.
In this lecture we shall trace the development of an integrated circuit from
an invention of the transistor to the microprocessor. We shall discuss the
impact of these inventions on our society that was to get an unrestricted
access to computing and information.
What are integrated circuits?
If we carefully strip an integrated circuit of its plastic shell, we shall see a
small rectangular surface–the chip itself–with a number of metal leads con-
nected to it.
Fig. 2. Inside a chip. Source: The Chipmakers, Time-Life Books (1988).
2 These leads are used to power the chip and to communicate with it. To
unravel the secret of a chip, we must place the chip under a microscope.
Under high magniﬁcation, a chip is a ﬂat area covered with tiny electronic
components interconnected with ﬂat ribbon-like wires (or paths). The ma-
jority of these electronic components are transistors – minuscule electronic
switches, that play the same role as vacuum tubes or electromagnetic switches
in early computers. The main advantages of transistors over other switches
is that they can be made small, million of times smaller than vacuum tubes
used to build the ENIAC.
Fig. 3. The chip revealed: this chip contains thousands of transistors deposited
on a tiny piece of silicon. Photograph by Ioan Sameli.
3 Fig. 4. Transistors inside Intel’s ﬁrst microprocessor – the 4004; the 4004 chip had
2,3000 transistors deposited on 2mm by 3mm piece of silicon. Source: http://www.4004.com
What’s a transistor?
The transistor is an electronic switch that allows or disallows the ﬂow of elec-
trical current through it. Vacuum tubes and electromagnetic relays can do
that as well but transistors are tiny, highly-reliable, fast, and require small
amounts of energy to operate. In addition, we have learned how to construct
electronic circuits with millions of them residing on little surfaces of silicon.
In 1971, the Intel 4004 processor–the most complex electronic device put
together–had 2,300 transistors. In 2010, an Intel Core processor held 560
million transistors, enough to build approximately 30,000 ENIACs on a sin-
gle chip! (Recall that the ENIAC was built of about 19,000 vacuum tubes).
4 The transistor’s invention was, as it is usually the case with inventing, not an
a sudden occurrence of a brilliant idea. There were various people involved
in various periods of time. Some even claim that the transistor’s origin lies in
technology recovered by the US Air Force from an alien spacecraft recovered
at Roswell, New Mexico in 1947. What can be said without any doubts is
that it was the work done at Bell Labs by William Shockley, John Bardeen,
and Walter Brattain at the end of the 1940s that kick-started a transistor-
powered revolution in electronics and created the foundations for our present
day digital reality.
Fig. 5. The Bell Lab’s prototype transistor. Source: unknown.
5 Fig. 6. 1973 envelope cover commemorating Bell Labs W. Shockley, J. Bardeen,
and W. Brattain’s Nobel Prize award for their work on the transistor. Source:
6 Brief Time-line of the Transistor:
1925-28: Physicist Julius Lilienfeld patented his transistor in Canada and U.S.
He did not provide a prototype or working application.
1947: William Shockley, John Bardeen, and Walter Brattain, physicists at
Bell Laboratories, created the ﬁrst working transistor (still large).
1952: The ﬁrst transistor-based commercial product: hearing aids from Sono-
tone, Maico, and Acousticon.
1953: First transistor radios: before laptops and smartphones of today they
were the most popular electronic communication device in history.
1953: The University of Manchester Transistor Computer (experimental).
1955: IBM introduced a transistor-based IBM 608 calculator replacing a sim-
ilar device, the 604, built with 1,200 vacuum tubes. The 608 used 2,200
transistors, was much smaller, used 95% less energy and was very reli-
Fig. 7. A variety of transistors, c. 1970s-90s. Source: unknown.
7 Fig. 8. A 1955 ad for Raytheon 8-transistor radio. Source: unknown.
8 The transistor was also a promise of a new era in the consumer electronics
industry. In just a few years from the transistor’s creation, the device deliv-
ered on its promise: not only it replaced vacuum tubes in radios, TV sets,
audio equipment, computers and all sorts of other electronic devices but also
allowed the manufacturing of new, highly reliable equipment in areas such
as health, automotive, and space sciences.
The transistor revolutionized both the concept design and manufacturing.
It allowed the development of miniaturized, portable, batter-powered elec-
tronic products that could withstand mechanical shock and vibration and
operate for years without defect.
Fig. 9. A 1964 ad for RCA transistors. Source: unknown.
9 Fig. 10. A 1957 ad for Admiral transistor-based consumer electronics products.
10 The more transistors the better...
In the early 1950s, as transistors were getting smaller and faster, many in the
electrical engineering community envisioned an electronic device that would
integrate several discrete components (transistors, diodes, resistors, capaci-
tors) into a circuit by, ﬁrst, making all of them of a single chip of silicon and,
then, interconnecting them with wires laid on the surface of the chip.
In 1968, Jack Kilby, an engineer at Texas Instruments (TI), build such a
device–the ﬁrst integrated circuit–and TI announced the chip’s ”discovery”
in January 1959. In recognition of his work, Kilby work was awarded Nobel
Prize in physics and was even commemorated on post stamps.
Fig. 11. A Marshall Islands stamp (left) and a US stamp (right) commemorating
Kilby’s invention of the integrated circuit.
11 In 1959, Kilby’s ideas were improved by Robert Noyce (of Fairchild) who also
used the concept of a ”ﬂat” transistor invented by Jean Hoerni at Fairchild
to build his circuits. Noyce demonstrated how to integrate several transistors
and other components on a ﬂat area of silicon without interconnecting wires.
His work resulted in the prototype of all modern integrated circuits.
Fig. 12. Robert Noyce and his 1959 integrated circuit (magniﬁed!!) with 4 tran-
sistors. Source: The Chipmakers, Time-Life Books (1988).
In 1961, both Fairchild and TI had a technology to manufacture integrated
circuits with tens of transistors on them. The demand from the US military,
space program and, soon after, computer industry, made circuit development
and manufacturing a very proﬁtable business for both companies.