(20點)What is TRANSISTOR ？
What is TRANSISTOR ？
- estelle leeLv 51 0 年前最佳解答
When a p-type semiconductor region is placed adjacent to an n-type region, they form a diode, and the region of contact is called a p-n junction. Combinations of such junctions are used to make transistors and other semiconductor devices whose electrical behavior can be controlled by the appropriate electrical stimuli.
The BJT is a three-terminal device consisting of 3 layers of alternating n- and p-type materials referred to as the emitter, base, and collector. Its structure basically consists of two back-to-back diodes, one between the emitter and base and the other between the base and collector.
There are two types of bipolar transistor: the NPN and the PNP. The transistor may be operated in three different regions: saturation, cut-off, and active. A transistor is said to be saturated if both its base-collector and base-emitter junctions are forward biased. Under this mode, the transistor is already completely 'on', i.e., the collector current is already very high and no longer increases appreciably even if more current is fed into the base. A transistor is in the cut-off region if both of its junctions are reverse biased. Under this mode, the transistor is 'off'', i.e., the collector current is very low. A transistor being used as a switch is operated alternately between saturation and cut-off regions. A transistor in the active region exhibits a change in collector current that is proportional to the change in base current.
The Metal-Oxide Semiconductor Field Effect Transistor (MOSFET) or MOS transistor is a type of transistor that consists of a metal layer, an oxide layer, and a semiconductor layer. The MOS transistor consists of three terminals: a gate, a source, and a drain. These are equivalent to the base, emitter, and collector of a bipolar transistor. The metal layer of the MOS transistor serves as the gate, while the source and drain are fabricated on the silicon substrate.
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2006-02-22 18:15:24 補充：
The transistor is one kind of semiconductor devices which includes BJT, MOSFET, JFET,...etc. Especially,MOSFET is basically a building block in modern integrated circuits.
Unlike the passive devices, the transistor is an active device which provides the functions of amplification and switching.
2006-02-22 18:17:14 補充：
2006-02-22 18:26:00 補充：
MOSFET is a four-terminal transistor,i.e.source(S),drain(D),gate(G)and substrate(B). MOSFET uses the so-called "field effect" which can control the current in the channel by the applied voltage on the gate.