Rather, a transistor modulates the energy flowing from a battery or power supply in a way that is similar to a valve adjusting the flow rate from a source of pressurized water. When a transistor acts as an amplifier it does not create the additional energy appearing in its output signal, just as a valve does not create water it dispenses. Vacuum tubes, which were developed before transistors but perform the same functions, are termed “valves ” in British usage in reference to this analogy. A small, varying force applied to the valve -a back-and-forth wiggle -causes matched variations in the greater force carried by the water passing through the pipe a small signal thus generates another that varies identically in time but is larger in amplitude. Transistor amplification can be compared to controlling a powerful flow of water through a pipe by turning a valve: in this analogy, the force applied to the valve represents the transistor ’s control voltage, while the water flowing through the pipe represents its output current. This increase in amplitude or strength is called amplification, one of the most basic processes in electronics. This current can in turn be converted into a voltage by passing it through a resistor (a passive or unpowered circuit device that simply dissipates energy) the change in voltage across this “load ” resistor can be many times greater than the change in voltage that was used to alter the resistance of the transistor itself. The resulting change in resistance between the other two terminals of the transistor -through one of which current enters the transistor, leaving through the other -changes the current passed through the transistor. The term transistor is a shortening of TRANSfer ResISTOR.Ī transistor can perform a variety of useful electrical tasks because its resistance (the ease with which an electrical current flows through it) can be adjusted using a low-power control signal applied to one of a transistor ’s three metallic terminals. To the extent that our civilization has come to depend on computers and electronic communications, therefore, it depends on the transistor. Virtually all electronic devices contain transistors, from a handful to hundreds of millions. Transistors are active devices, meaning that they must be supplied with power to function. To make a transistor, a semiconducting crystal is selectively contaminated with other elements, such as arsenic, phosophorus, boron, or gallium.Ī transistor is controlled by voltages communicated to it through three or more metallic contacts. Most transistors are made using the unique semi-conducting properties of silicon or germanium (most often silicon). The significance and future of the transistorĪ transistor is a small, solid device capable of amplifying electrical signals or switching them on and off. Common base, common emitter, and common-collector configurations
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