In an n-p-n transistor operating in the active region, the emitter-base junction is forward biased and electrons are injected into the base region. They are useful in amplifier because the currents at the emitter and collector are controllable by a relatively small base current. These transistors are current regulating devices that control the amount of current flowing them in proportion to the amount of biasing voltage applied to their base terminal-acting like a current- controlled switch. These three terminals are known and labeled as Emitter, Base and Collector. The Bipolar Transistor basic construction consists of two PN-junctions producing three connecting terminals with each terminal bring given a name to identify it from the other two. Transistors amplifiers are commonly used in applications like RF (radio frequency), audio, OFC (optic fibre communication) and the like. It can produce a strong er output signal, a voltage or current, which is proportional to a weaker input signal that is, it can act as an amplifier. Because controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. An electrical signal can be amplified by using a device which allows a small current or voltage to control the flow of a much larger current from a dc power source. ![]() It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. It is a semiconductor device used to amplify or switch electronic signals and electrical power. Transistors are a key component to many amplifying circuits. ![]() Applications of amplifier are of wide range, they are mainly used in communications, controllers, audio and video instruments. It is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. An amplifier is a device for increasing the power of a signal. Amplification is a process of increasing the signal strength by increasing the amplitude of a given signal without changing its characteristics. It uses electric power from a power supply to increase the amplitude of a signal. The strategies are identified as classes of amplifiers ranging from Class A to Class G. An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power of a signal (a time-varying voltage or current). 2.5.2 Amplifier Efficiency Transistor amplifiers use several different biasing strategies.
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