( July 2012) ( Learn how and when to remove this template message)īJTs exist as PNP and NPN types, based on the doping types of the three main terminal regions. Please help improve it to make it understandable to non-experts, without removing the technical details. This section may be too technical for most readers to understand. The arrow on the symbol for bipolar transistors indicates the p–n junction between base and emitter and points in the direction in which conventional current travels. In this article, current arrows are shown in the conventional direction, but labels for the movement of holes and electrons show their actual direction inside the transistor. On the other hand, inside a bipolar transistor, currents can be composed of both positively charged holes and negatively charged electrons. Because electrons carry a negative charge, they move in the direction opposite to conventional current. However, current in metal conductors is generally due to the flow of electrons. Specialized types are used for high voltage switches, for radio-frequency (RF) amplifiers, or for switching high currents.īy convention, the direction of current on diagrams is shown as the direction that a positive charge would move. Bipolar transistors are still used for amplification of signals, switching, and in mixed-signal integrated circuits using BiCMOS.
Hundreds of bipolar junction transistors can be made in one circuit at very low cost.īipolar transistor integrated circuits were the main active devices of a generation of mainframe and minicomputers, but most computer systems now use CMOS integrated circuits relying on field-effect transistors. Diffused transistors, along with other components, are elements of integrated circuits for analog and digital functions. The superior predictability and performance of junction transistors quickly displaced the original point-contact transistor. The junctions can be made in several different ways, such as changing the doping of the semiconductor material as it is grown, by depositing metal pellets to form alloy junctions, or by such methods as diffusion of n-type and p-type doping substances into the crystal. A bipolar transistor allows a small current injected at one of its terminals to control a much larger current flowing between the terminals, making the device capable of amplification or switching.īJTs use two p–n junctions between two semiconductor types, n-type and p-type, which are regions in a single crystal of material. In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier. From top to bottom: TO-3, TO-126, TO-92, SOT-23ģD model of a TO-92 package, commonly used for small bipolar transistorsĪ bipolar junction transistor ( BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. If you get into any trouble then ask in comments and I will try my best to resolve your issues.Typical individual BJT packages. If you are working on this transistor then I would suggest you to first design its Proteus Simulation, as its always the best strategy to work on simulation before working on hardware, as you can sort out all the problems beforehand. So, that was all about this Bipolar Junction transistor named as 2N3904. There are numerous applications of 2N3904 and is most commonly used in projects where below conditions are required: A small current on the P doped layer transforms into a higher current on other two terminals.Collector layer is bigger in size than the other two layers and thus highly doped.The centred layer is very small in size and is low concentrated as compared to the other two N doped layers.These 3 layers are different from each other in terms of size and concentration of doping.single P doped layer embedded between two N doped layers. Collector-Base Voltage Vcbo of 2N3904 is 60V.Emitter-Base Voltage Vebo of 2N3904 is 6V.Collector-Emitter Voltage Vceo of this transistor is 40V.Maximum voltage rating of 2N3904 is 40V.Maximum current rating of this BJT transistor is 200mA.2N3904 is a current controlled transistor and that's why comes in the category of Bipolar Junction Transistors, abbreviated as BJT.You should also have a look at 2N3904 Pinout, if you are planning to work on this transistor. In a few embedded circuits, its also used as a switch.
It's an NPN transistor which is normally used for fast switching and amplification purposes. In today's tutorial, I am going to share basic information of 2N3904.
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