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An amplifier does just what its name suggests – amplify, or send and receive signals. However, there are many different types of amplifiers and the way each of them work is different in its own ways. Usually, when an amplifier is spoken of, we usually mean that is increases the power of a signal; but it can do other things too, besides amplifying. Most often, signals that are amplified in radio and communications are not sine waves. For this discussion, let us assume that a sine wave of alternating voltage is being amplified using SAW filters. A full cycle of alternating signals is equivalent to 360 degrees. If that concept is used, it is easier to describe each fraction of the cycle. For example, if a full cycle of 360 degrees sine wave with alternating current is transmitted to a rectifier, only half of it, 180 degrees, will be seen at the output. Therefore, a half-wave rectifier is explained as one that has an operating angle of 180 degrees. In the same way, different amplifier types will output only a certain percentage of the amplified input signal. This concept is very often a hard one to grasp. This is because in some cases like an audio amplifier IC for example, we want exactly what goes in to come out but in a louder version. However, when it comes to radio circuits, there are several other considerations; one of the main being the efficiency of the amplifier. An audio amplifier IC usually has a very low efficiency but there are many ways in which this can be improved. As mentioned before, amplifiers come in many different types. Let us discuss briefly the use of a class D amplifier IC. This is a switching amplifier where its power devices are all operated as binary switches. These switches cannot be on and off at the same time. They are either only on or only off at any given time. There should be absolutely no time spent in the transition between the on and off states. A variable duty cycle wave is generated from a class D amplifier IC. The low-frequency part of this spectrum is usually the output signal required and the high frequency portion only needs to convert the wave-form into binary so that amplification can take place by switching the power devices. The output stages in devices like pulse generators are examples of class D amplifiers. Yet, the term is used mostly for power amplifiers with the intention to reproduce signals that has a bandwidth much below the switching frequency.
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Saw filters, Audio amplifier IC, Class D amplifier IC,
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