TRANSISTOR-THE KING OF ELECTRONICS

We know, the flow of electrons is electric current. Electrons are said to be negative charge carriers.

In a molecular structure, if there is a vacancy for an electron, it is called hole. When an electron from somewhere in the structure fills-up this hole, a new hole will be created where the electron has just left. Hence a hole can move opposite to the electron. So the holes are said to be positive charge carriers.

In a germanium crystal, arsenic is infused. We get electron rich material called N type (negative) material. When boron is added to germanium, we get holes surplus P type (positive) substance.

A thin P type material is sandwiched between two N type material. Now a transistor is made. These three pieces NPN are respectively called emitter, base, and collector.

By connecting negative of the battery to the emitter(N) and positive to the collector(N), the electrons can be pushed from emitter and pulled at the collector. On the way, through the base(P) some electrons combine with holes. So some electrons are lost in the base. But most of the electrons reach collector resulting in collector current.

By applying suitable negative voltage to the base, we can control the quantity of holes in the base region. consequently the loss of electrons flowing through the base and the collector current is also controlled.

In a nutshell: By varying small voltage that is applied to the base, one can produce big variations in the collector current. This is amplification, main function of transistor.

Example of one application: Microphone(mic) converts voice into electrical signals. These small varying electric voltage is fed to the base of the transistor. Then we get large varying current as output from the collector. It is then supplied to a speaker which produces big sound.

So many transistors are present in all the electronic gadgets. In the CPU of the computer, millions of transistors is present.
At present : No transistor, no electronics.

Note: PNP transistor is also possible.

Comments

THE EARTH, A SUPER ORGANISM

JOIN MY COURSE: "Become a programmer in a day with python" A man called 'love lock' (what a name) proposed a theory called Gaia theory, named after Greek Goddess. It says, "Earth is a self-regulating organism like a human being. The organic life in it interacts with in-organic matter and maintains atmosphere, temperature and environment". Hence the earth is still suitable for the life to thrive. Imagine, in a particular place, there are lot of flowers. Some flowers are white and some are darkly coloured. We know, white reflects light and heat while dark absorbs the same. White flowers can thrive in hot climate. But dark flowers requires cold climate. The absorption and reflection balances and the environment reaches average, warm temperature at which both the flowers can co-exist. This is the essence of "Gaia" theory. On our earth, ...

DISORDER IS THE "ORDER OF THE DAY"

Imagine a balloon full of air. The air molecules are moving randomly inside the balloon. Let us pierce the balloon with a pin. The air rushes out. Why should not the air molecules stay inside the balloon safely and ignore the little hole? That is not the way the world works. The molecules always "want to occupy as many states as possible". Hence the air goes out in the open to occupy more volume. The things always goes into disorder (entropy) and the disorder increases with time. The above statement is what we call "second law of thermodynamics". Consider a cup of coffee on the table. Suppose the heat from entire room flows to your cup of coffee, the coffee will boil and the rest of the room will freeze. Freezing means bringing things to order and arrangement. It violates the second law. Hence it will never happen. Hence heat must flow from high ...

CASINO'S GAME

Let us find out how the casino survives with mathematics. Say, your friend invite you for a game of dice. You must bet (wager) 2 dollars. If you roll 'six' you will get back 8 dollars. The game will go on for 30 rounds. All sounds good. The probability of rolling 'six' is 1/6. Since the game will be played for 30 times, the 'expected win' is 30*1/6 = 5. That is, you are expected to win 5 rounds out of 30. Hence your gain will be 5 * 8 =40 dollars. ok. This also implies that you will loose 25 rounds. Hence your loss will be 25*2 =50 dollars. Your net gain will be gain-less = 40-50 = -10 dollars. For 30 rounds, the loss is -10 dollars, Hence, for one round =-10/30 = -1/3 dollars. There will be a loss of -1/3 or 0.33 dollars per round. It is not a fair game. Let us make a simple formula to calculate 'Pa...

sciencecapsules

Search This Blog