A Bipolar Junction
Transistor (BJT) has three terminals connected to three doped semiconductor
regions. In an NPN transistor, a thin and lightly doped P-type material is
sandwiched between two thicker N-type materials; while in a PNP transistor, a
thin and lightly doped N-type material is sandwiched between two thicker P-type
materials.
In the following we will only consider NPN BJTs.
In many schematics of
transistor circuits (especially when there exist a large number of transistors
in the circuit), the circle in the symbol of a transistor is omitted.
All previously considered components (resistor,
capacitor, inductor, and diode) have two terminals (leads) and can therefore be
characterized by the single relationship between the current going through and
the voltage across the two leads. Differently, a transistor is a three-terminal
component, which could be considered as a two-port network with an input-port
and an output-port, each formed by two of the three terminals, and
characterized by the relationships of both input and output currents and
voltages.
Depending on which of the three terminals is used as
common terminal, there can be three possible configurations for the two-port
network formed by a transistor: common emitter (CE), common base (CB), and
common collector (CC). Here we only consider CE and CB, as CC is not widely
used.
Depending on which of the three terminals is used as common terminal, there can be three possible configurations for the two-port network formed by a transistor: common emitter (CE), common base (CB), and common collector (CC). Here we only consider CE and CB, as CC is not widely used.
Tidak ada komentar:
Posting Komentar