Minggu, 03 April 2011

How transistors work

Transistors are semiconductor devices used as an amplifier, a circuit breaker and

junction (switching), voltage stabilization, signal modulation, or as other functions.

Such transistors can function electric valves, where according to input current (BJT) or

input voltage (FET), allowing a very accurate electrical conduction from the circuit source

Through-hole transistors (compared with the measuring tape centimeter)

In general, the transistor has three terminals. Voltage or current that is placed in one

terminal set larger currents through two other terminals. Transistors are

a very important component in modern electronic world. In a series of analog, transistor

used in the amplifier (booster). Series analog surround speakers, a power source

stable, and the radio signal booster. In digital circuits, transistors used

as high-speed switch. Some transistors can also be arranged in such a way

that function as logic gates, memory and other components.

How it works semiconductor

In essence, transistors and vacuum tubes have similar functions, both regulate

the amount of electrical current flow.

To understand the workings of semiconductors, for example a glass of pure water. If the pair

conductor is inserted into it, and given the right under voltage DC voltage electrolysis

(Before the water turned into hydrogen and oxygen), there will be no current flows due to water

do not have a charge carrier (charge carriers). Thus, pure water is considered as an insulator.

If a little salt inserted into it, the conduction current will begin to flow, because

a number of free charge carrier (mobile carriers, ion) is formed. Raising the salt concentration will

improve conduction, but not much. Salt itself is a non-conductor (insulator),

because the carrier muatanya not free.

Pure silicon itself is an insulator, but if some contaminants are added, such as

Arsenic, by a process called doping, in quantities small enough

do not mess up the layout of the silicon crystal, Arsenic will provide free electrons and

results allow the conduction of electrical current. This is due to Arsenic has 5 atoms in

outer orbit, while the silicon is only 4. Conduction occurs because the free charge carrier has

added (by the excess electrons from Arsenic). In this case, an n-type silicon (n

to negative, because the charge carriers are negatively charged electrons) has


In addition, silicone can be mixed with boron to create p-type semiconductor. Because

Boron only has 3 electrons in the outer orbit, a new carrier, named

"Holes" (holes, positive charge carrier), will be formed in the layout of the silicon crystal.

In vacuum tubes, charge carrier (electron) will be emitted by thermionic emission from

a cathode which is heated by a wire filament. Therefore, it can not make a hollow tube

positive charge carriers (holes).

Can be listened to that same charge carrier charged will repel each other, so that

without any other style, cargo carriers will be distributed evenly

in semiconductor materials. But in a bipolar transistor (or diode junction)

where a p-type semiconductor and an n-type semiconductors are made in a single chip

silicon, charge carriers tend to move toward the PN connection

(The boundary between p-type semiconductor and n-type), attracted by the charge

opposite of the opposite.

The increase of the amount of pollutant (doping level) will increase the conductivity of the material

semiconductors, provided that the layout of the silicon crystal is maintained. In a transistor

bipolar, emitter terminal region has a larger number of doping than

terminal base. The ratio between the emitter and base doping is one of many

factors that determine the nature of the strengthening of current (current gain) of the transistor.

The amount required of a semiconductor doping is very small, the size of one

compared to one hundred million, and is the key to the success of the semiconductor. In a

metal, the population is very high charge carrier, single carrier for each atom.

In the metal, to change the metal into the insulator, the charge carriers must be swept away by installing

a voltage difference. In metal, this stress is very high, much higher than that capable

destroy it. However, in a semiconductor there is only one charge carrier in

several million atoms. The number of voltage required to sweep the charge carrier in a number of

of semiconductors can be achieved easily. In other words, electricity in the metal is

inkompresible (can not be compressed), like fluid. While in the semiconductor, electrical

are such that gas can be compressed. Semiconductors with doping can be converted into

insulator, while the metal is not.

The picture above describes the conduction is caused by the charge carrier, ie electrons or

hole, but it is basically a bipolar transistor action activities of these carriers

to cross the depletion zone. Depletion zone is formed by the transistor

were given reverse bias voltage, the applied voltage between the base and

emitter. Although transistor looks like is formed by two diode connected, a

transistor itself can not be made by connecting two diodes. To make the transistor,

sections should be made from a piece of crystalline silicon, with a regional base

very thin.

How transistors work

Of the many types of modern transistors, initially there are two basic types of transistors, bipolar

junction transistor (BJT or bipolar transistor) and field-effect transistor (FET), which

each works differently.

Bipolar transistor so named because its main conduction channel using the two polarities

carriers: electrons and holes, to carry electrical current. In the BJT, the main electric current

must pass through a region / boundary layer called the depletion zone, and the thickness of this layer

can be set with high speed in order to regulate the flow of the mainstream.

FET (also called a unipolar transistor) using only one type of charge carrier (electron

or holes, depending on the type FET). In the FET, the main electric current flows in one channel

narrow conduction with the depletion zone on both sides (as compared with bipolar transistor

where the base is cut off the main electric current direction). And thickness of this border area

can be changed by changing the applied voltage, to change the thickness of the channel conduction

them. See article for each type for further explanation.

In general, the transistor can be differentiated based on many categories:

* Semiconductor material: Germanium, Silicon, Gallium arsenide
* Physical Packaging: Through Hole Metal, Plastic Through Hole, Surface Mount, IC, etc.

development of the transistor that is IC (Integrated Circuit) and others.
* Polarity: NPN or N-channel, PNP or P-channel
* Maximum power capacity: Low Power, Medium Power, High Power
* Maximum working frequency: Low, Medium, or High Frequency, RF transistors, Microwave, and

* Applications: Amplifiers, Switches, General Purpose, Audio, High Voltage, etc.

BJT (Bipolar Junction Transistor) is one of two types of transistors. How it works BJT

can be thought of as two diodes are positive or negative terminal huddle, so that

There are three terminals. The three terminals are emitter (E), collector (C), and base (B).

Changes in electrical current in small quantities in the terminal base can produce changes in current

large amounts of electricity to the collector terminal. This principle underlies the use of

transistor as an amplifier electronics. The ratio between the current in the stream at the base koletor

usually denoted by ß or HFE. ß usually hover around 100 for

transisor BJT transistor.

FET is divided into two families: Junction FET (JFET) and Insulated Gate FET (IGFET) or too

known as Metal Oxide Silicon (or Semiconductor) FET (MOSFET). In contrast to the IGFET,

JFET gate terminal in the form of a diode with the channel (semiconductor material between

Source and Drain). In its function, this makes the N-channel JFET into a version

solid-state of vacuum tubes, which also forms a diode between the grid and cathode.

And also, both (JFET and vacuum tubes) work in "depletion mode", both have

high input impedance, and both deliver electrical currents under voltage control inputs.

FET further divided into type enhancement mode and depletion mode. Mode indicates

polarity of the gate voltage compared to the current source FET to conduct electricity. If

we take the N-channel FET as an example: in the depletion mode, the gate is negative compared

by source, while the enhancement mode, the gate is positive. For both modes, if

gate voltage is made more positive, current flow between source and drain will increase.

For P-channel FET, all polarities reversed-polarity. Most of the IGFET is a type

enhancement mode, and almost all the JFET is a depletion mode type.

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