# How transistors work – Gokul J. Krishnan

Modern computers
are revolutionizing our lives, performing tasks unimaginable
only decades ago. This was made possible by a long series
of innovations, but there’s one foundational invention
that almost everything else relies upon: the transistor. So what is that, and how does such a device enable
all the amazing things computers can do? Well, at their core, all computers
are just what the name implies, machines that perform
mathematical operations. The earliest computers were manual
counting devices, like the abacus, while later ones used mechanical parts. What made them computers was having
a way to represent numbers and a system for manipulating them. Electronic computers work the same way, but instead of physical arrangements, the numbers are represented
by electric voltages. Most such computers use a type of math
called Boolean logic that has only two possible values, the logical conditions true and false, denoted by binary digits one and zero. They are represented by high
and low voltages. Equations are implemented
via logic gate circuits that produce an output of one or zero based on whether the inputs satisfy
a certain logical statement. These circuits perform three fundamental
logical operations, conjunction, disjunction, and negation. The way conjunction works is an “and gate”
provides a high-voltage output only if it receives
two high-voltage inputs, and the other gates work
by similar principles. Circuits can be combined to perform
complex operations, like addition and subtraction. And computer programs
consist of instructions for electronically performing
these operations. This kind of system needs a reliable
and accurate method for controlling electric current. Early electronic computers,
like the ENIAC, used a device called the vacuum tube. Its early form, the diode, consisted of two electrodes
in an evacuated glass container. Applying a voltage to the cathode
makes it heat up and release electrons. If the anode is at a slightly
higher positive potential, the electrons are attracted to it, completing the circuit. This unidirectional
current flow could be controlled by varying the voltage to the cathode, which makes it release more
or less electrons. The next stage was the triode, which uses a third electrode
called the grid. This is a wire screen
between the cathode and anode through which electrons could pass. Varying its voltage makes it either repel or attract the electrons
emitted by the cathode, thus, enabling fast current-switching. The ability to amplify signals
also made the triode crucial for radio and long distance communication. But despite these advancements,
vacuum tubes were unreliable and bulky. With 18,000 triodes, ENIAC was nearly
the size of a tennis court and weighed 30 tons. Tubes failed every other day, and in one hour, it consumed the amount
of electricity used by 15 homes in a day. The solution was the transistor. Instead of electrodes,
it uses a semiconductor, like silicon treated
with different elements to create an electron-emitting N-type, and an electron absorbing P-type. These are arranged in three
alternating layers with a terminal at each. The emitter, the base, and the collector. In this typical NPN transistor, due to certain phenomena
at the P-N interface, a special region called a P-N junction
forms between the emitter and base. It only conducts electricity when a voltage exceeding
a certain threshold is applied. Otherwise, it remains switched off. In this way, small variations
in the input voltage can be used to quickly switch between
high and low-output currents. The advantage of the transistor lies
in its efficiency and compactness. Because they don’t require heating,
they’re more durable and use less power. ENIAC’s functionality can now be surpassed
by a single fingernail-sized microchip containing billions of transistors. At trillions of calculations per second, today’s computers may seem like
they’re performing miracles, but underneath it all, each individual operation is still
as simple as the flick of a switch.

## 100 thoughts to “How transistors work – Gokul J. Krishnan”

1. Nak Tan says:

To fans of Fallout games, Fallout is set in an alternate earth that has never invented the transistor. They only use vacuum tubes, which is why computers were huge.

2. Moon Knight Productions says:

basically a lightbulb

3. ryehaaan says:

i didnt know logic circuits are made of transistor… :/ and i also i didnt know each gate AND OR has thier own name haha. thanks ted ed now i know ๐

4. camron me says:

Yea, but tubes are warmer doooood

5. HeapTV says:

Very good explanation !

6. Alp Aktuna says:

Very well-explained.

7. Antone Alpha says:

huh?

8. Noyz Productions says:

wow

9. Add859 TankiOnline says:

10. tygonmaster says:

The HIGH and LOW voltages thing is a bit misleading here. Yes, 1 is typically a high signal and 0 a low one, but it depends if the system is active HIGH or active LOW. In other words, 0 can be HIGH and vice versa. Additionally, LOW is very rarely represented by a voltage of 0 as how does one know if the machine is working if there is no voltage? It is doing the same thing it is doing as if it is off. As such, LOW is usually a voltage of 1V, 2V, or some other lower voltage (or, again, HIGH can be represented this way as long as you are consistent.) You just need a difference in voltage for the system to work. Just a fun fact for everyone. ๐

11. Warren Day says:

So when a charge passes through a transistor this can be determined as a 0 or a 1 creating binary; but what is actually controlling the voltage? How is it turned on or off?

12. Muhammad Fauzan Ridho says:

i studied it in electrical engineering for about 4 years total. And now they compressed it into 4.53 minutes video, amazing LoL

13. Badreddine Baim says:

Making me feel stupid ๐ thank you =D

14. Snowman Star says:

I love how TED Ed ends their videos. Gives me chills every time.

15. Diaa Ilayan says:

marvelous

16. Vishwa Mithra says:

Didn't you miss the part at 3:50 to 4:10, you comfortably skipped the logic behind the switching. And the animation is inaccurate, as it showing the electrons being stopped at the base emitter junction and not the base collector junction. Sorry but what my books told me was the base and emitter in this configuration are always forward biased. Please correct me if I had made a mistake(Regardless the animation is outstanding).

17. TheFunnyBuddy says:

What makes computers tick?

Broken components. You shouldn't be hearing ticks from your computer.

18. RideRedRacer says:

this is so cool.

19. Simple Brian says:

This was the one device that was never invented in the fallout universe… If memory serves, No pun intended

20. Flamer Gamer says:

you forgot relays

21. Saikat Sharma says:

Learn lot of thanks

22. ProneToInfection says:

Didn't Tesla invent the transistor? Or at least had the basic idea in his patents

23. Alden says:

I have always wondered why a computer even knows what an operating system tells it

24. Fifi O'Neil says:

minecraftia!

25. jess jesse says:

1: bassiccally transister are made of : zinc & copper & silicon = 3 diferent tiny plates ! Which plates doing what & power volt? Right dude?

26. jess jesse says:

1: wholly circuitboard = copper & silver & gold & zinc dreads! Called magnetic-powers out your nature !

27. Supreme Tuber says:

superb

28. Nikhil Raj says:

Just simply amazing……

29. SuperMe29 - says:

I still dont get it, why do you need those logic gate and what create the bits

30. blesyl67 says:

As a person who is currently studying Analogue Electronic and Digital Electronics , your animation and information on how Transistors work is 10x better than what my college teaches us . Hope you could expand more into this topic !

31. Panie says:

a clock

32. Iceypumpkin head says:

So basically a computer is a 1 0 machine

33. Nelly Benbradey says:

Transistors are in clocks

34. Nelly Benbradey says:

Transistor Is In Clock ? It Analog

35. Just in Y. says:

Very well explained,maybe depeltion layer could have been represented.

36. ying ma says:

37. Da CV Artificial Intelligence says:

You've done a great job. I'd been looking for this precious video thanks for giving us.

38. MANUEL ADRIAN LIMON GARAY says:

PLEASE MAKE MORE VIDEOS LIKE THIS , about computers , networking, storage , etc. You guys are awesome!!!!!

39. Arunima Maiti says:

Can you put the Video for 5th graders

40. Maithri Ashokan says:

I loved this video so much!

41. Erick Posada restrepo says:

I still don't know how transistor works.

42. kondomonster says:

Love to see how you tackle transistor theory.

43. kondomonster says:

You explained it better than my instructors at Aviation Electronics Technician school while I was in the Navy.

44. Rafael Pontes says:

Great simplified video.

45. M Ucar says:

great

46. JetbyGaming says:

Background music sucks

47. ๋ฐ์๋ฏผ says:

Vecum tube:Gold bug
Transistor:Just do it!

48. faizan imran says:

Doping

49. ้ผ้ทๅ says:

Brilliant

50. Ace Gaming says:

Hii my name is also Gokul

51. Christian Nicholas says:

WHAT MAKES COMPUTER THICC

52. Lera Leush says:

This explanation is so short and lacking… sigh

53. kyle bachman says:

I wish my IQ was higher so i could understand this better

54. Olie Manuel says:

๐๐๐

55. Sunny shah says:

It's sad to see that an Engineer who builds these amazing technology makes less money than the Kardashians

56. jayyfan says:

but whats the device that controls the voltage at 3:59 to either make electrons pass or not pass?

57. Kotelypiesely Kuziak says:

idk just pls dont burn my amplifier ๐
01101001 01100100 01101011 00100000 01101010 01110101 01110011 01110100 00100000 01110000 01101100 01110011 00100000 01100100 01101111 01101110 01110100 00100000 01100010 01110101 01110010 01101110 00100000 01101101 01111001 00100000 01100001 01101101 01110000 01101100 01101001 01100110 01101001 01100101 01110010 00100000 00111010 00101000

58. GrapheneCarbide says:

the transistor is obsolete. we now have microprocessors. that are much better.

59. Caleb Sousa says:

TICC

60. Alan Ramirez says:

Shoutout to Tesla?

61. Tech guy says:

The most important thing i learned from this video is some transistors are friendly and wave to you when viewed under a microscope.

62. Beta Bilim says:

You need to create an academia !

63. Ukasha Mohamed says:

Is it only me !!
Or didn't you guys understand that too ??

IS THAT A MAC

65. Gamma Light says:

Oh

66. Gamma Light says:

I have a feeling computers will evolve to processing in temperature variations, measuring fractions of trillionths of a degree instead of mass raw voltage alone. Ex. Water (or some liquid) that freezes at X rate with Y pattern produces Z code with E sequence. Liquid quantum computing. Less thermal breakdown if the liquid medium is developed to remain thermostatic at a broad range of ambient temperature. Salt water is already conductive and who knows, maby the byproduct of computing produces hydrogen fuel to power itself.. The answers are probably over complicated. Aliens man, aliens..

67. Angus Duffy says:

Right Iโve been stuck on this for ages now. Iโve done my research and still havenโt found an answer. How does a computer alter the voltage to a transistor, because surely it must switch between a high and low voltage constantly to change the output of a transistor?

68. Namutolo Stephen says:

Thanks a lot guys

69. Allah lover says:

Amazing sir ๐

70. Leto85 says:

Hm, I feel dissapointment that I didn't really get this.

71. Matt Stiles says:

U still didnt explain how the binary is done

72. napabar says:

You forgot all about relay computers, which precede tube computers.

73. ShowTech Guides says:

I get it

74. learn english easily ุชุนูู ุงูุงูุฌููุฒูุฉ ุจุณูููุฉ says:

Those vedios are great and helpful

75. Don Noviel eL Natividad says:

Discussion on transisitors starts at 3:24.

76. Vance McCarthy says:

Next lesson. How does on/off states write and run programs. As in machine language.

77. Mohamed Shabaan says:

AMAZING <3

78. aryan garg says:

treat to watch all the best for future

79. Eun Sik Park says:

Wow! Computers have become so advanced. It's amazing what people have developed.

80. Bell10 says:

TED without stage โperformanceโ is an advancement. However the hooked on background โmusicโ disturbs and distracts from listening more, than the soundmixer/producer could ever imagine. The soundtrack does not contribute content, it simply spoils the content. Pls delete that track if possible and reupload. Thanks for the vid.

81. Bilal Alhatmi says:

There are a lot of questions in my imagination and I need someone to answer me about them We in Yemen live a lot of loss and most of us live in an illusion They do not know about science Thank you for the programs you offer for the truth seekers Thank you thank you

82. Akiva Shmalo says:

Loved the video. Wouldve been nice if you included some history behind these inventions, like the name of the inventors!

83. Navratan Yadav says:

please make a vedio on
semiconductor
๐๐ป๐๐ป๐๐ป๐๐ป๐๐ป๐๐๐๐๐

84. Funny Memes says:

Oh wow… just saw TED ad right at the beginning of this video… first time I saw it…

85. Mount Olympus says:

Sometimes I feel learning science is very much important. People who choose commerce or humanities are never going to know how this world works. From quantum physics , astronomy, computer programming, engineering, hardware, chemistry, mathematics, bio technology, …. everything is done in science.

86. Anurag Mishra says:

1:24 and I thought Mathematical Reasoning was the most useless chapter.

87. Merlin says:

alien technology
#roswell

88. Maysam Mirzakhalili says:

I enjoyed it a lot – thank you .

89. Duvall Johnson says:

The treating of silicon with other elements to create an electron emitting N-type and an electron absorbing P-type is know as doping. It's used to create conductance. Since the outer shell of silicon is 4 valence electrons, it's easy to fill silicon's outer shell with other silicon atoms. This makes conductance hard. So, some silicon atoms are replaced.

90. mohamed ayman says:

Thanks a lot for explaining.

91. Cooper D says:

How many of you watch BE MY GUEST DUBAI AD OF SHAHRUK KAN. hit like if you are a die hard khan fan

92. Delta Frost says:

Why Momo is so thicccckkkk

93. Akina Hachi Roku says:

Sooo, millions of transistors are shouting either yes or no. How does that make my computer process something??

94. Abdul Ghani says:

cool xplanation

95. Arek Rozmarynowicz says:

Please tell me me more about computers! These videos are awesome

96. sweiland75 says:

This was far more thorough than I expected. Well done.

97. Its me Ceo says:

Awesome

98. Dorothy Isidro says:

They protecc
They attacc
But most importantly
They like to clicc bacc

99. Evelene Maye says:

If your computer is ticking then theres probably something foreign in your fans. Or you have very loud harddrives