If the amplifier doesn't faithfully reproduce Ideally, it has to produce a reasonably flat response or linear response with a wide range ofĭifferent input signals (so the gain is pretty much constant across a

Of frequencies over which it works satisfactorily is called itsīandwidth. In both frequency and amplitude (for an audio amplifier, that meansĪn audio amplifier might work better with some sound frequencies than others the range Input signal even when that signal is constantly (and sometimes dramatically) varying The hard bit is that it must faithfully reproduce the quality of the Now the key thing about an amplifier is not just that it boosts an electric current. Photo by Denise Rayder courtesy of US Air Force. It's a type of probe that can test a circuit without direct electrical contact and works through electromagnetic induction, a bit like Photo: Testing telephone circuits with an inductive amplifier. For audio (sound) amplifiers, the gain is often expressed inĭecibels (specifically, it's ten times the logarithm of the output power divided by the input power). So anĪmplifier that doubles the size of the original signal has a gain ofĢ. (or sometimes the gain factor or amplification factor). Signal to the input signal, a measurement called the gain of an amplifier It's easy to calculate how much difference an amplifier makes: it's the ratio of the output Placed inside your ear canal so you hear a much-magnified version of A transistor-based amplifier takes the signal (the input)Īnd boosts it many times before feeding it into a tiny loudspeaker Sounds from the world around you and convert them into a fluctuatingĮlectric current (a signal) that constantly changes in Wear a hearing aid, you'll know it uses a

Photo by courtesy of the Science Museum, London, published on Wikimedia Commons under a Creative Commons Licence (CC BY-SA 2.0).Īn amplifier (often loosely called an 'amp') is an electromagnetic orĮlectronic component that boosts an electric current. Photo: A home-made Williamson vacuum tube (valve) amplifier from around 1949, built from a magazine article to a design by D T N Williamson. Loudspeakers and the huge black boxes you plug intoĮlectric guitars to make them raise the roof. They're also the gadgets in radios that boostįaraway signals and the devices in stereo equipment that drive your Match, you will understand the concept of amplification.'Īmplifiers are the tiny components in hearing aids that make voices Mule with the energy expended by yourself in the striking of the If you then compare the energy expended shortly thereafter by the

William Shockley, Nobel-Prize winning co-inventor of the transistor (a revolutionaryĮlectronic amplifier dating from the 1940s) had a vivid way ofĮxplaining it: 'If you take a bale of hay and tie it to the tail ofĪ mule and then strike a match and set the bale of hay on fire, and

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