Transistors

This time we'll discuss a little about the transistors, the transistor is a semiconductor device 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 voltage input (FET), allowing a very accurate electrical conduction of the electrical source circuit.

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


In general, the transistor has three terminals. Voltage or current that is placed on one terminal set larger currents through two other terminals. Transistors are the essential components in modern electronic world. In analog circuitry, the transistor used in the amplifier (booster). Series analog surround speakers, stable electricity sources, and radio signal amplifier. In digital circuits, transistors used as high-speed switch. Some transistors can also be arranged in such a way as to function as logic gates, memory and other components.
How transistors work
Of the many types of modern transistors, initially there are two basic types of transistors, bipolar junction transistors (BJT or bipolar transistor) and field-effect transistor (FET), each of which works differently.
Bipolar transistor so named because its main conduction channel using two polarity 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 adjusted 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 hole, depending on the type FET). In the FET, the main electric current flowing in a narrow conduction channel by 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 conduction channel. See the article for each type for further explanation


The types of transistors

Transistor symbols of Various Types
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.
• Type: UJT, BJT, JFET, IGFET (MOSFET), IGBT, HBT, MISFET, VMOSFET, MESFET, HEMT, SCR and the development of the transistor that is IC (Integrated Circuit) and others.
• Polarity: NPN or N-channel, PNP or P-channel
• Maximum capacity: Low Power, Medium Power, High Power
• Maximum working frequency: Low, Medium, or High Frequency, RF transistors, Microwave, etc.
• Applications: Amplifiers, Switches, General Purpose, Audio, High Voltage, etc.

BJT
BJT (Bipolar Junction Transistor) is one of two types of transistors. How it works BJT can be imagined 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 electrical currents in large numbers at the collector terminal. This principle underlies the use of transistors as electronic amplifier. The ratio between the current in koletor with the current at the base is usually denoted by β or HFE. β typically ranges from about 100 to transistor-transisor BJT.

FET
FET is divided into two families: Junction FET (JFET) and Insulated Gate FET (IGFET) or also known as Metal Oxide Silicon (or Semiconductor) FET (MOSFET). In contrast to the IGFET, the gate terminal of JFET forms a diode with the channel (semiconductor material between the Source and Drain). In its function, this makes the N-channel JFET into a solid-state version of the vacuum tube, which also forms a diode between the grid and cathode. And also, both (JFET and vacuum tubes) work in "depletion mode", both have a high input impedance, and both deliver electrical currents under voltage control inputs.
FET further divided into type enhancement mode and depletion mode. Mode indicates the 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 to the source, while the enhancement mode, the gate is positive. For both modes, if the gate voltage is made more positive, current flow between source and drain will increase. For P-channel FET, all polarities reversed-polarity. Most are the type enhancement mode IGFET, and almost all the JFET is a depletion mode type.