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Three frequently encountered solid-state components are shown here. Starting from the top: a circuit chip that is about an inch long, a red light-emitting diode, and a transistor.Solid-state electronic devices are an integral part of modern life. The transistor, first developed in 1947 by Bell Labs, became the first commercially available solid-state device in the 1960s. These devices have largely replaced vacuum tubes in most electronic devices. While vacuum tubes are still found in the transmitters of radio stations, many guitar amplifiers, and certain audiophile equipment, they differ from solid-state devices as they tend to burn out and break more easily.
The crystal radio was among the first solid-state devices. In this device, a piece of wire placed on a crystal's surface effectively separates the lower-frequency audio from the higher-frequency radio carrier wave. This is made possible by the crystal's ability to allow current to flow in only one direction. For more information, check out How Radio Works.
The term 'solid-state' originates from the way electrical signals travel through solid semiconductor materials. Before the advent of solid-state devices like the transistor, electricity would flow through various components inside a heated vacuum tube. Solid-state devices, such as transistors, use conductors to regulate signal flow within circuits.
- In a transistor amplifier, even a small change in the input signal's amplitude leads to a corresponding larger amplitude output from the transistor.
- In a vacuum tube amplifier, after the tube has warmed up, a signal is introduced to the tube's 'grid,' and the resulting output is the same frequency but with a significantly higher amplitude.
A transistor's sandwich-like structure, consisting of the emitter, base, and collector, performs a similar function but at much lower DC voltages, with no need for any 'warm-up' time. In digital circuits, an integrated circuit chip is essentially a collection of transistors interconnected by wires.
Solid-state devices called diodes have replaced rectifier vacuum tubes that were once used to convert alternating current (AC) into direct current (DC). Low-heat light-emitting diodes (LEDs), another type of solid-state device, are now used as indicators on devices like your computer and monitor, replacing older incandescent bulbs. Multiple bright LEDs are also used in the third stoplight of many U.S. vehicles and in traffic signals.
Solid-state miniature electronic components can be found in numerous devices and applications:
- Mounted on flexible, thin-film printed circuits in devices such as cameras and disk drives.
- The beeping sound produced by cell phones, pagers, or car alarm systems.
- The voice chip found in answering machines.
- The remote control for your television.
- A laser pointer device.
- The internal components of an MP3 player.
- A quartz watch.
- The image sensor inside a digital camera or camcorder.
- The monitor you're looking at right now.
- The mouse you're using to navigate through this page!
Check out the following links for further details on solid-state electronics.
