The Junction Transistor A bipolar junction transistor consists of three regions of doped semiconductors. A small current in the center or base region can be used to control a larger current flowing between the end regions (emitter and collector). The device can be characterized as a current amplifier, having many applications for amplification and switching.
Index Semiconductor concepts Semiconductors for electronics Electronics concepts
Constraints on operation Transistor operating conditions Varieties of Transistors Details about conduction in transistors Determining collector current Details about base-emitter junction HyperPhysics***** Condensed Matter
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Transistor as Current Amplifier The larger collector current IC is proportional to the base current IB according to the relationship IC =βIB , or more precisely it is proportional to the base-emitter voltage VBE . The smaller base current controls the larger collector current, achieving current amplification. Index Semiconductor concepts Semiconductors for electronics Electronics concepts
The analogy to a valve is sometimes helpful. The smaller current in the base acts as a "valve", controlling the larger current from collector to emitter. A "signal" in the form of a variation in the base current is reproduced as a larger variation in the collector-to-emitter current, achieving an amplification of that signal.
Reference Diefenderfer /Holton p156
Constraints on operation Comments on structure To pnp version HyperPhysics***** Condensed Matter
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Transistor Structure
Index Semiconductor concepts Semiconductors for electronics Electronics concepts
The junction transistor Current amplifier operation Constraints on operation HyperPhysics***** Condensed Matter
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Transistor as Current Amplifier The larger collector current IC is proportional to the base current IB according to the relationship IC =βIB , or more precisely it is proportional to the base-emitter voltage VBE . The smaller base current controls the larger collector current, achieving current amplification.
Index Semiconductor concepts Semiconductors for electronics Electronics concepts
Constraints on operation To npn version HyperPhysics***** Condensed Matter
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Constraints on Transistor Operation Index Semiconductor concepts Semiconductors for electronics Electronics concepts
The bold text and the "buttons" are active links to further details. HyperPhysics***** Condensed Matter
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Transistor Maximum Values Index Part of the manufacturer's data for transistors is a set of maximum values which must not be exceeded in its operation. These form some of Semiconductor the constraints on transistor operation which are a part of the design of concepts any circuit. A typical set, for the silicon transistor 2N2222: Semiconductors • Collector-Base Voltage = 60 v for electronics • Collector-Emitter Voltage = 30 v • Base-Emitter Voltage = 5 v Electronics concepts • Power dissipation = 500 mW •
Temperature 125 C