electronic switch

(electronics) Vacuum tube, crystal diodes, or transistors used as an on and off switching device. Test instrument used to present two wave shapes on a single gun cathode-ray tube.

An electronic device in which one or more input signals can be routed to one or more outputs by the application of the appropriate electrical control signals. The term is most often applied when analog signals are involved, but the terminology is occasionally used when digital signals are involved.

Conceptually, an electronic switch can be visualized as a group of one or more mechanical electrical switches (such as light switches used in commercial wiring or toggle switches used in many electronic control panels) in which, instead of mechanically opening or closing the contacts, the physical opening and closing is achieved by applying appropriate electrical control signals to separate terminals on the switch in much the same way that a relay performs. The electronic switch does not contain mechanical contacts but semiconductor devices such as bipolar junction transistors or field-effect transistors. The basic electronic switch is depicted in illus. a. A and B are the terminals of the switch. When a control signal is applied to V_C, the switch closes. When the electronic switch is closed, a small residual resistance R_s remains between the terminals as depicted in the simple model of illus. b. The value of this resistance is termed the on resistance. In most applications the nonzero on resistance does not prove problematic, but the user needs to be aware of this limitation. The electronic switch is typically bidirectional in the sense that the terminals A and B are interchangeable. See also Electric switch; Relay; Transistor.

Switching devices. (a) Symbol for electronic switch. (b) Simple model of electronic switch.

Electronic switches can be very small, allowing a large number of these devices to be placed in a small area they can be very fast, with on and off response times which are orders of magnitude faster than can be achieved with mechanical counterparts; and they are considerably more reliable over a large number of cycles than their mechanical counterparts.

An on/off switch activated by electrical current.

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