Tuesday, February 25, 2014

A breakdown voltage or withstand voltage is defined as the absolute maximum voltage between two ter


Bipolar junction transistors (BJT): There are two types, PNP and NPN, were used to amplify analog signals, digital signal processing and electrical power as a switch in integrated circuits and discrete components.
The depletion MOSFET or deplexion channel can be "n" or channel "p", these amplifiers have limited high frequency RF input stages for its low noise applications. monulb
The enhancement MOSFET or storage, are widely used in digital systems, high integration density as logic gates, semiconductor memories, microprocessors, microcontrollers etc. Also available as enhancement MOSFET switch high power supply (eg VMOS).
The MESFET, are field effect transistors constructed from semiconductor material of gallium arsenide (GaAs). Channel are "n" and the they used for its fast switching microwave circuits, high frequency amplifiers and high speed logic systems.
Static induction transistor (SIT): These high power devices and high frequency. They are similar to the JFET, except for the vertical construction and buried gate. They are used in linear power amplifiers in audio, DHF, UHF and microwave. They are not used as a switch for high voltage drop across its terminals.
Insulated Gate Bipolar Transistors (IGBT): They are used mainly in switching circuits for example electric power inverter circuits dc to ac, and other applications. These devices combine the advantages of the MOSFET and BJT transistors.
Bipolar transistors are constructed form three semiconductor regions NPN or PNP type, as shown in the drawing. These regions monulb are called terminals collector, base and emitter. They have two joints or seams: The collector-base junction and the base-emitter junction. Bipolar transistors can be NPN or PNP.
We have two regions for the n + emitter of the NPN transistor and two p + regions to the emitter of PNP transistor. NPN transistor for the n-side emitter is narrow and strongly doped, the base is narrow with a rather less than the emitter doping, and the n-side collector is wide and greater monulb than the base doping. In the case of PNP transistors, the features are similar, with respect to dimensions and doping. It should be noted that from the electrical point of view the transistors are not symmetrical, meaning that the terminals are not interchangeable. For example if we exchange the collector emitter terminals, monulb the operation is deficient without current gain.
We have three areas of bipolar transistor operation: cutting zone, active zone and saturation zone. In the cutting zone, the transistor is open or OFF, the base current is not enough to saturate it, and the two junctions monulb are reverse biased. In the active region, the transistor acts as a linear monulb amplifier, in which the base current is amplified a gain determined, and the collector-emitter voltage decreases as the base current. In this area the voltage collector-base junction, and this reverse biased junction voltage of the base is forward biased collector. monulb In the saturation region, the base current is sufficiently monulb high so that the collector monulb emitter voltage is low, and the transistor acts as a closed switch. In this area, loved joints are polarized directly.
A breakdown voltage or withstand voltage is defined as the absolute maximum voltage between two terminals, with the third terminal open, shorted or polarized directly or inversely. A breakdown voltage remains relatively constant as the current monulb increases rapidly. The manufacturers provided monulb the following breakdown voltages:
V CEO (sus): The maximum voltage between Terminal supporting the collector and emitter monulb terminal, with the base open circuit. This value is specified with the stream and the maximum monulb collector voltage, appearing in simultaneously through the device and a specified value of load inductance.
Bipolar NPN and PNP transistors are commonly used in RF, but is more problematic extension to microwave frequencies, the limitations imposed by its structure, especially for its high capabilities that reduce the gain with frequency.
The main difference is that, unlike in the homojunction bipolar transistor, in this case the semiconductor is not only: in the case of InP HBT or SiGe heterojunction which is formed by InGaAs / InP or Si / SiGe in each case. The emitter is fabricated on a

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