transistor - the device working on semiconductors in the electronics.It is designed for the conversion and amplification of electrical signals.There are two types of devices: a bipolar transistor and a unipolar transistor, or a field.
If the transistor at the same time there are two kinds of charge carriers - holes and electrons, it is called bipolar.If the transistor is only one type of charge, it is unipolar.
Imagine the job of ordinary tap water.They turned the valve - the water flow increased, he turned to the other side - the flow has slowed or stopped.In practice, this is the principle of operation of the transistor.Only instead of water flowing through the flow of electrons.The operating principle of a bipolar transistor type is characterized in that in the electronic device are two types of current.They are divided into large or small and basic, or manager.And the power of the drive current affect the capacity of the primary.Consider a field effect transistor.The principle of it is different from the others.It takes only one current output which depends on the ambient electromagnetic field.
Bipolar transistor is made of 3 layers of a semiconductor, and, most importantly, the two PN-junctions.It should be distinguished PNP and NPN transitions and, therefore, and transistors.These semiconductors are alternating electron and hole conduction.
Bipolar transistor has three terminals.This base contact, leaving a central layer and two electrodes at the edges - emitter and collector.Compared to these extreme base electrode layer is very thin.Along the edges of the transistor region of the semiconductor is not symmetrical.For proper operation of the semiconductor device layer disposed on the collector side, must be let a little, but is thicker as compared with the side of the emitter.
principles of the transistor based on physical processes.Let's work with the model of PNP.The work will be similar NPN models, except the polarity of the voltage between such basic elements as the collector and emitter.It will be in the opposite direction.
Substance P type comprises a hole or positively charged ions.N-type substance composed of negatively charged electrons.In the considered transistor, the number of holes in P is much greater than the number of electrons in N.
When connecting the voltage source between such parts as the emitter and collector of the transistor principles are based on the fact that the holes are attracted to the pole and to gather near the emitter.But there is no current.The electrical field from the voltage source does not reach the collector because of the thick layer of the semiconductor emitter layer and the semiconductor base.
Then connect a voltage source with a different combination of elements, namely the base and emitter.Now hole directed to the base and begin to interact with the electrons.The central part of the base is saturated with holes.The result is a two currents.More - from the emitter to the collector, small - from the base to the emitter.
By increasing the voltage to the base in the layer N be the more holes to increase the base current, little effort emitter current.So a small change in base current is amplified seriously enough emitter current.The result is a growth signal bipolar transistor.
Consider the principles of the transistor depending on the mode of its operation.There are the normal active mode, inverse active mode, the saturation mode cutoff.
When active mode emitter junction is opened and closed collector junction.The inversion mode, everything is opposite.
