How transistors work - Gokul J. Krishnan

918,501 views ใƒป 2016-06-06

TED-Ed


ืื ื ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ืœืžื˜ื” ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ.

ืชืจื’ื•ื: Ido Dekkers ืขืจื™ื›ื”: Sigal Tifferet
00:06
Modern computers are revolutionizing our lives,
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ืžื—ืฉื‘ื™ื ืžื•ื“ืจื ื™ื™ื ืขื•ืฉื™ื ืžื”ืคื›ื” ื‘ื—ื™ื™ื ื•,
00:09
performing tasks unimaginable only decades ago.
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ืžื‘ืฆืขื™ื ืžืฉื™ืžื•ืช ืฉืœืคื ื™ ื›ืžื” ืขืฉื•ืจื™ื ื ืจืื• ื‘ืœืชื™ ืืคืฉืจื™ื•ืช.
00:13
This was made possible by a long series of innovations,
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ื–ื” ืืคืฉืจื™ ื‘ืฉืœ ืกื“ืจื” ืืจื•ื›ื” ืฉืœ ื—ื™ื“ื•ืฉื™ื,
00:17
but there's one foundational invention that almost everything else relies upon:
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ืื‘ืœ ื™ืฉ ื”ืžืฆืื” ื‘ืกื™ืกื™ืช ืื—ืช ืฉื›ืžืขื˜ ื›ืœ ื”ืฉืืจ ืชืœื•ื™ื•ืช ื‘ื”:
00:22
the transistor.
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ื”ื˜ืจื ื–ื™ืกื˜ื•ืจ.
00:24
So what is that,
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ืื– ืžื” ื–ื”,
00:25
and how does such a device enable all the amazing things computers can do?
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ื•ืื™ืš ื›ื–ื” ืžื›ืฉื™ืจ ืžืืคืฉืจ ืืช ื›ืœ ื”ื“ื‘ืจื™ื ื”ืžื“ื”ื™ืžื™ื ืฉืžื—ืฉื‘ื™ื ื™ื›ื•ืœื™ื ืœืขืฉื•ืช?
00:30
Well, at their core, all computers are just what the name implies,
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ื•ื‘ื›ืŸ, ื‘ื‘ืกื™ืกื, ื›ืœ ื”ืžื—ืฉื‘ื™ื ื”ื ืžื” ืฉื”ืฉื ืžืฆื™ืข,
00:34
machines that perform mathematical operations.
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ืžื›ื•ื ื•ืช ืฉืžื‘ืฆืขื•ืช ืคืขื•ืœื•ืช ืžืชืžื˜ื™ื•ืช.
00:37
The earliest computers were manual counting devices,
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ื”ืžื—ืฉื‘ื™ื ื”ืจืืฉื•ื ื™ื ื”ื™ื• ืžื›ื•ื ื•ืช ืกืคื™ืจื” ื™ื“ื ื™ื•ืช,
00:40
like the abacus,
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ื›ืžื• ื”ื—ืฉื‘ื•ื ื™ื”,
00:41
while later ones used mechanical parts.
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ื‘ืขื•ื“ ื”ืžืื•ื—ืจื™ื ื™ื•ืชืจ ื”ืฉืชืžืฉื• ื‘ื—ืœืงื™ื ืžื›ืื ื™ื™ื.
00:44
What made them computers was having a way to represent numbers
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ืžื” ืฉืขืฉื” ืื•ืชื ืžื—ืฉื‘ื™ื ื”ื™ื” ืฉื™ืฉ ืœื”ื ื“ืจืš ืœื™ื™ืฆื’ ืžืกืคืจื™ื
00:48
and a system for manipulating them.
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ื•ืžืขืจื›ืช ืœืคืขื•ืœ ืขืœื™ื”ื.
00:51
Electronic computers work the same way,
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ืžื—ืฉื‘ื™ื ืืœืงื˜ืจื•ื ื™ื™ื ืขื•ื‘ื“ื™ื ื‘ืื•ืชื” ื“ืจืš,
00:53
but instead of physical arrangements,
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ืื‘ืœ ื‘ืžืงื•ื ืืจื’ื•ืŸ ืคื™ื–ื™,
00:55
the numbers are represented by electric voltages.
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ื”ืžืกืคืจื™ื ืžื™ื•ืฆื’ื™ื ืขืœ ื™ื“ื™ ืžืชื—ื™ื ื—ืฉืžืœื™ื™ื.
00:58
Most such computers use a type of math called Boolean logic
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ืจื•ื‘ ื”ืžื—ืฉื‘ื™ื ืžืฉืชืžืฉื™ื ื‘ืกื•ื’ ืžืชืžื˜ื™ ืฉื ืงืจื ืœื•ื’ื™ืงื” ื‘ื•ืœื™ืื ื™ืช
01:02
that has only two possible values,
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ืฉื‘ื” ื™ืฉ ืจืง ืฉื ื™ ืขืจื›ื™ื ืืคืฉืจื™ื™ื,
01:04
the logical conditions true and false,
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ื”ืžืฆื‘ื™ื ื”ืœื•ื’ื™ื™ื ืืžืช ืื• ืฉืงืจ,
01:07
denoted by binary digits one and zero.
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ืฉืžืฆื•ื™ื™ื ื™ื ืขืœ ื™ื“ื™ ื”ืกืคืจื•ืช ื”ื‘ื™ื ืืจื™ื•ืช ืื—ืช ื•ืืคืก.
01:11
They are represented by high and low voltages.
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ื”ืŸ ืžื™ื•ืฆื’ื•ืช ืขืœ ื™ื“ื™ ืžืชื— ื’ื‘ื•ื” ื•ื ืžื•ืš.
01:14
Equations are implemented via logic gate circuits
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ืžืฉื•ื•ืื•ืช ืžื™ื•ืฉืžื•ืช ื“ืจืš ืžืขื’ืœื™ ืฉืขืจ ืœื•ื’ื™
01:17
that produce an output of one or zero
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ืฉืžื™ื™ืฆืจื™ื ืคืœื˜ ืฉืœ ืื—ื“ ื•ืืคืก
01:21
based on whether the inputs satisfy a certain logical statement.
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ื‘ื”ืชื‘ืกืก ืขืœ ืื ื”ืงืœื˜ ืžืจืฆื” ื”ืฆื”ืจื” ืœื•ื’ื™ืช ืžืกื•ื™ื™ืžืช.
01:25
These circuits perform three fundamental logical operations,
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ื”ืžืขื’ืœื™ื ื”ืืœื” ืžื‘ืฆืขื™ื ืฉืœื•ืฉ ืคืขื•ืœื•ืช ืœื•ื’ื™ื•ืช ื‘ืกื™ืกื™ื•ืช,
01:28
conjunction, disjunction, and negation.
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ื—ื™ื‘ื•ืจ, ืื•, ื•ืฉืœื™ืœื”.
01:32
The way conjunction works is an "and gate" provides a high-voltage output
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ื”ื“ืจืš ื‘ื” ื—ื™ื‘ื•ืจ ืขื•ื‘ื“ ื”ื™ื "ืฉืขืจ ื•" ืฉืžืกืคืง ืคืœื˜ ื‘ืžืชื— ื’ื‘ื•ื”
01:36
only if it receives two high-voltage inputs,
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ืจืง ืื ื”ื•ื ืžืงื‘ืœ ืฉื ื™ ืžืชื—ื™ื ื’ื‘ื•ื”ื™ื,
01:40
and the other gates work by similar principles.
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ื•ื”ืฉืขืจื™ื ื”ืื—ืจื™ื ืขื•ื‘ื“ื™ื ืœืคื™ ืขืงืจื•ื ื•ืช ื“ื•ืžื™ื.
01:43
Circuits can be combined to perform complex operations,
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ืžืขื’ืœื™ื ื™ื›ื•ืœื™ื ืœื”ื™ื•ืช ืžืฉื•ืœื‘ื™ื ื›ื“ื™ ืœื‘ืฆืข ืžืฉื•ื•ืื•ืช ืžื•ืจื›ื‘ื•ืช,
01:46
like addition and subtraction.
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ื›ืžื• ื—ื™ื‘ื•ืจ ื•ื—ื™ืกื•ืจ.
01:48
And computer programs consist of instructions
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ื•ืชื•ื›ื ื•ืช ืžื—ืฉื‘ ืžื›ื™ืœื•ืช ื”ื•ืจืื•ืช
01:51
for electronically performing these operations.
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ืœื‘ื™ืฆื•ืข ืืœืงื˜ืจื•ื ื™ ืฉืœ ื”ืคืขื•ืœื•ืช ื”ืืœื•.
01:54
This kind of system needs a reliable and accurate method
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ืกื•ื’ื™ื ื›ืืœื” ืฉืœ ืžืขืจื›ื•ืช ืฆืจื™ื›ื•ืช ืฉื™ื˜ื” ืืžื™ื ื” ื•ืžื“ื•ื™ื™ืงืช
01:58
for controlling electric current.
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ืœืฉืœื™ื˜ื” ืขืœ ื–ืจืžื™ื ืืœืงื˜ืจื•ื ื™ื™ื.
02:00
Early electronic computers, like the ENIAC,
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ืžื—ืฉื‘ื™ื ืืœืงื˜ืจื•ื ื™ื™ื ืžื•ืงื“ืžื™ื, ื›ืžื• ื” ENIAC,
02:02
used a device called the vacuum tube.
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ื”ืฉืชืžืฉื• ื‘ืžื›ืฉื™ืจ ืฉื ืงืจื ืฉืคื•ืคืจืช ื•ืืงื•ื.
02:05
Its early form, the diode,
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ื”ืฆื•ืจื” ื”ืžื•ืงื“ืžืช ืฉืœื”, ื”ื“ื™ื•ื“ื”,
02:07
consisted of two electrodes in an evacuated glass container.
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ื”ื›ื™ืœื” ืฉืชื™ ืืœืงื˜ืจื•ื“ื•ืช ื‘ืžื™ื›ืœ ื–ื›ื•ื›ื™ืช ืžืคื•ื ื”.
02:12
Applying a voltage to the cathode makes it heat up and release electrons.
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ื”ืคืขืœืช ืžืชื— ืขืœ ื”ืงื˜ื•ื“ื” ื’ื•ืจืžืช ืœื” ืœื”ืชื—ืžื ื•ืœืฉื—ืจืจ ืืœืงื˜ืจื•ื ื™ื.
02:17
If the anode is at a slightly higher positive potential,
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ืื ื”ืื ื•ื“ื” ื‘ืคื•ื ื˜ืฆื™ืืœ ื—ื™ื•ื‘ื™ ื’ื‘ื•ื” ื‘ืžืขื˜,
02:20
the electrons are attracted to it,
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ื”ืืœืงื˜ืจื•ื ื™ื ื ืžืฉื›ื™ื ืืœื™ื”,
02:22
completing the circuit.
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ื•ืžืฉืœื™ืžื™ื ืืช ื”ืžืขื’ืœ.
02:24
This unidirectional current flow could be controlled
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ื”ื–ืจื ื”ื—ื“ ื›ื™ื•ื•ื ื™ ื”ื–ื” ื™ื›ื•ืœ ืœื”ื™ืฉืœื˜
02:27
by varying the voltage to the cathode,
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ืขืœ ื™ื“ื™ ืฉื™ื ื•ื™ ื”ืžืชื— ื‘ืงืชื•ื“ื”,
02:29
which makes it release more or less electrons.
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ืžื” ืฉื’ื•ืจื ืœื” ืœืฉื—ืจืจ ื™ื•ืชืจ ืื• ืคื—ื•ืช ืืœืงื˜ืจื•ื ื™ื.
02:33
The next stage was the triode,
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ื”ืฉืœื‘ ื”ื‘ื ื”ื™ื” ื˜ืจื™ื•ื“ื”,
02:34
which uses a third electrode called the grid.
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ืฉืžืฉืชืžืฉืช ื‘ืืœืงื˜ืจื•ื“ื” ืฉืœื™ืฉื™ืช ืฉื ืงืจืืช ื”ื’ืจื™ื“.
02:37
This is a wire screen between the cathode and anode
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ื–ื” ืžืกืš ื—ื•ื˜ื™ ื‘ื™ืŸ ื”ืงื˜ื•ื“ื” ืœืื ื•ื“ื”
02:41
through which electrons could pass.
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ื“ืจื›ื• ื”ืืงืœื˜ืจื•ื ื™ื ื™ื›ื•ืœื™ื ืœืขื‘ื•ืจ.
02:43
Varying its voltage makes it either repel
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ืฉื™ื ื•ื™ ื”ืžืชื— ืฉืœื” ื’ื•ืจื ืœื” ืื• ืœื“ื—ื•ืช
02:46
or attract the electrons emitted by the cathode,
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ืื• ืœืžืฉื•ืš ืืช ื”ืืœืงื˜ืจื•ื ื™ื ืฉืžื•ืคืฆื™ื ืขืœ ื™ื“ื™ ื”ืงื˜ื•ื“ื”,
02:49
thus, enabling fast current-switching.
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ืœื›ืŸ, ื–ื” ืžืืคืฉืจ ืžื™ืชื•ื’ ืžืชื— ืžื”ื™ืจ.
02:52
The ability to amplify signals also made the triode crucial for radio
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ื”ื™ื›ื•ืœืช ืœื”ื’ื‘ื™ืจ ืืช ื”ืื•ืช ื”ืคื›ื” ืืช ื”ื˜ืจื™ื•ื“ื” ืœื—ื™ื•ื ื™ืช ื’ื ืœืจื“ื™ื•
02:57
and long distance communication.
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ื•ืชืงืฉื•ืจืช ืœื˜ื•ื•ื— ืืจื•ืš.
03:00
But despite these advancements, vacuum tubes were unreliable and bulky.
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ืื‘ืœ ืœืžืจื•ืช ื”ื”ืชืงื“ืžื•ื™ื•ืช ื”ืืœื•, ืฉืคื•ืคืจื•ืช ื•ืืงื•ื ื”ื™ื• ืžื’ื•ืฉืžื•ืช ื•ืœื ืืžื™ื ื•ืช.
03:04
With 18,000 triodes, ENIAC was nearly the size of a tennis court
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ืขื 18,000 ื˜ืจื™ื•ื“ื•ืช, ENIAC ื”ื™ื” ื›ืžืขื˜ ื‘ื’ื•ื“ืœ ืฉืœ ืžื’ืจืฉ ื˜ื ื™ืก
03:09
and weighed 30 tons.
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ื•ืฉืงืœ 30 ื˜ื•ืŸ.
03:11
Tubes failed every other day,
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ืฉืคื•ืคืจื•ืช ื›ืฉืœื• ื›ืœ ื™ื•ื ื›ืžืขื˜,
03:13
and in one hour, it consumed the amount of electricity used by 15 homes in a day.
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ื•ื‘ืฉืขื” ืื—ืช, ื”ื•ื ืฆืจืš ื›ืžื•ืช ื—ืฉืžืœ ืฉ 15 ื‘ืชื™ื ืฆื•ืจื›ื™ื ื‘ื™ื•ื.
03:19
The solution was the transistor.
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ื”ืคื™ืชืจื•ืŸ ื”ื™ื” ื”ื˜ืจื ื–ื™ืกื˜ื•ืจ.
03:21
Instead of electrodes, it uses a semiconductor,
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ื‘ืžืงื•ื ืืœืงื˜ืจื•ื“ื•ืช ื”ื•ื ื”ืฉืชืžืฉ ื‘ืžื•ืœื™ื›ื™ื ืœืžื—ืฆื”,
03:24
like silicon treated with different elements
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ื›ืžื• ืกื™ืœื™ืงื•ืŸ ืฉืžื˜ื•ืคืœ ื‘ื™ืกื•ื“ื•ืช ืฉื•ื ื™ื
03:26
to create an electron-emitting N-type,
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ื›ื“ื™ ืœื™ืฆื•ืจ ืกื•ื’ N ืžืฉื’ืจ ืืœืงื˜ืจื•ื ื™ื,
03:29
and an electron absorbing P-type.
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ื•ืืœืงื˜ืจื•ื“ืช P ืกื•ืคื’ืช ืืœืงื˜ืจื•ื ื™ื.
03:32
These are arranged in three alternating layers
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ืืœื” ืžืกื•ื“ืจื•ืช ื‘ืฉืœื•ืฉ ืฉื›ื‘ื•ืช ืžืชื—ืœืคื•ืช
03:35
with a terminal at each.
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ืขื ื˜ืจืžื™ื ืœ ื‘ื›ืœ ืื—ืช.
03:37
The emitter, the base, and the collector.
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ื”ืžืฉื“ืจ, ื”ื‘ืกื™ืก, ื•ื”ืื•ืกืฃ.
03:39
In this typical NPN transistor,
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ื‘ืกื•ื’ ืžืกื•ื™ื™ื ื–ื” ืฉืœ ื˜ืจื ื–ื™ืกื˜ื•ืจ NPN,
03:42
due to certain phenomena at the P-N interface,
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ื‘ืฉืœ ืชื•ืคืขื” ืžืกื•ื™ื™ืžืช ื‘ืžืžืฉืง ื” P-N,
03:45
a special region called a P-N junction forms between the emitter and base.
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ื”ืื–ื•ืจ ื”ืžื™ื•ื—ื“ ืฉื ืงืจื ืฆื•ืžืช P-N ื ื•ืฆืจ ื‘ื™ืŸ ื”ืžืฉื“ืจ ืœื‘ืกื™ืก.
03:50
It only conducts electricity
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ื”ื•ื ืžื•ืœื™ืš ื—ืฉืžืœ ืจืง
03:52
when a voltage exceeding a certain threshold is applied.
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ื›ืฉื”ืžืชื— ืฉืžืคืขื™ืœื™ื ืขื•ื‘ืจ ืกืฃ ืžืกื•ื™ื™ื.
03:56
Otherwise, it remains switched off.
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ืื—ืจืช, ื”ื•ื ื ืฉืืจ ื›ื‘ื•ื™.
03:58
In this way, small variations in the input voltage
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ื‘ื“ืจืš ื–ื•, ืฉื™ื ื•ื™ื™ื ืงืœื™ื ื‘ืžืชื— ื”ืงืœื˜
04:02
can be used to quickly switch between high and low-output currents.
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ื™ื›ื•ืœื™ื ืœื”ื™ื•ืช ื‘ืฉื™ืžื•ืฉ ื›ื“ื™ ืœื”ื—ืœื™ืฃ ื‘ืžื”ื™ืจื•ืช ื‘ื™ืŸ ืžืชื— ืงืœื˜ ื’ื‘ื•ื” ืœื ืžื•ืš.
04:07
The advantage of the transistor lies in its efficiency and compactness.
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ื”ื™ื™ืชืจื•ืŸ ืฉืœ ื”ื˜ืจื ื–ื™ืกื˜ื•ืจ ื ืžืฆื ื‘ื™ืขื™ืœื•ืช ื•ื‘ืงื•ืžืคืงื˜ื™ื•ืช.
04:12
Because they don't require heating, they're more durable and use less power.
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ื‘ื’ืœืœ ืฉื”ื ืœื ื“ื•ืจืฉื™ื ื—ื™ืžื•ื, ื”ื ื™ื•ืชืจ ืขืžื™ื“ื™ื ื•ืžืฉืชืžืฉื™ื ื‘ืคื—ื•ืช ื—ืฉืžืœ.
04:16
ENIAC's functionality can now be surpassed by a single fingernail-sized microchip
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ื”ื™ื•ื ืžื™ืงืจื• ืฆ'ื™ืค ื‘ื•ื“ื“ ื‘ื’ื•ื“ืœ ืฆื™ืคื•ืจืŸ ืฉืžื›ื™ืœ ืžืœื™ื•ื ื™ ื˜ืจื ื–ื™ืกื˜ื•ืจื™ื.
04:22
containing billions of transistors.
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ื™ื›ื•ืœ ืœืขื‘ื•ืจ ืืช ื”ืคื•ื ืงืฆื™ื ืœื™ื•ืช ืฉืœ ENIAC
04:24
At trillions of calculations per second,
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ื‘ื˜ืจื™ืœื™ื•ื ื™ ื—ื™ืฉื•ื‘ื™ื ืœืฉื ื™ื”,
04:27
today's computers may seem like they're performing miracles,
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ื”ืžื—ืฉื‘ื™ื ืฉืœ ื”ื™ื•ื ื ืจืื™ื ื›ืื™ืœื• ื”ื ืžื‘ืฆืขื™ื ื ื™ืกื™ื,
04:30
but underneath it all,
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ืื‘ืœ ื‘ื‘ืกื™ืกื,
04:31
each individual operation is still as simple as the flick of a switch.
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ื›ืœ ืคืขื•ืœื” ื‘ื•ื“ื“ืช ืขื“ื™ื™ืŸ ืคืฉื•ื˜ื” ื›ืžื• ืœื—ื™ืฆื” ืขืœ ืžืชื’.
ืขืœ ืืชืจ ื–ื”

ืืชืจ ื–ื” ื™ืฆื™ื’ ื‘ืคื ื™ื›ื ืกืจื˜ื•ื ื™ YouTube ื”ืžื•ืขื™ืœื™ื ืœืœื™ืžื•ื“ ืื ื’ืœื™ืช. ืชื•ื›ืœื• ืœืจืื•ืช ืฉื™ืขื•ืจื™ ืื ื’ืœื™ืช ื”ืžื•ืขื‘ืจื™ื ืขืœ ื™ื“ื™ ืžื•ืจื™ื ืžื”ืฉื•ืจื” ื”ืจืืฉื•ื ื” ืžืจื—ื‘ื™ ื”ืขื•ืœื. ืœื—ืฅ ืคืขืžื™ื™ื ืขืœ ื”ื›ืชื•ื‘ื™ื•ืช ื‘ืื ื’ืœื™ืช ื”ืžื•ืฆื’ื•ืช ื‘ื›ืœ ื“ืฃ ื•ื™ื“ืื• ื›ื“ื™ ืœื”ืคืขื™ืœ ืืช ื”ืกืจื˜ื•ืŸ ืžืฉื. ื”ื›ืชื•ื‘ื™ื•ืช ื’ื•ืœืœื•ืช ื‘ืกื ื›ืจื•ืŸ ืขื ื”ืคืขืœืช ื”ื•ื•ื™ื“ืื•. ืื ื™ืฉ ืœืš ื”ืขืจื•ืช ืื• ื‘ืงืฉื•ืช, ืื ื ืฆื•ืจ ืื™ืชื ื• ืงืฉืจ ื‘ืืžืฆืขื•ืช ื˜ื•ืคืก ื™ืฆื™ืจืช ืงืฉืจ ื–ื”.

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