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Introduction (this page, see below)
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Few electronics systems would be of much use without signals of some sort flowing through them. Sometimes the signal is an electrified version of some non-electronic parameter. For example, a PA amplifier system uses voice and other sound signals converted into electrical form by a microphone. An electronic light meter’s signal is the electrical equivalent of the intensity of the light shining on some sort of photo- sensor.
Often, though, the signals needed are purely electronic in origin. The circuitry must create its own signals from scratch. There are countless types of electrical signals that we might want to generate. Simply put, an electronically-generated signal may be either a dc voltage or current, or an ac waveform of some type. Both dc and ac signal generation are covered thoroughly in this guide. Section 1 deals with dc signals, and the rest of the guide explores various ac signals, including the most popular and widely used—the sine wave ( section 2), the rectangle wave and its special forms, the square wave and the pulse wave (section 3), the triangle wave, the saw tooth wave, and the staircase wave.
Odd and exotic special purpose waveforms are also covered, along with white noise and pink noise. Function generators, which can generate two or more different waveforms within a single circuit, are discussed in section 4. White-noise and pink- noise generators are the subjects of section 6.
Section 7 explores various ways to generate nonstandard, complex ac wave forms. Amplitude modulation, frequency modulation, additive synthesis and sub tractive synthesis are among the techniques discussed here. The special problems and considerations involved when working with RF (radio frequency) signals are explored in section 7.
Finally, section 8 examines the various, and often surprising ways that ac signals can be generated by digital circuitry. Usually digital circuitry only works with rectangle waves of some sort, but techniques for digitally synthesizing other analog waveforms will also be considered in this section.
In addition to the theoretical background and circuit design tips, this guide also features sixteen inexpensive but useful projects, including sound generators, power supplies, and test equipment. Certainly, none of these projects will put any commercial manufacturers of such equipment out of business. For the most part, we won’t be dealing with super-precision specifications in any of these projects. But the specs are still surprisingly good for such easy, minimal-cost projects. They should be good enough for most typical hobbyist applications. The limitations of any given project will be mentioned in the text, where relevant.
You can spend hundreds of dollars to buy a deluxe commercial signal generator. Or, you can build any one of these projects for less than $50, and it will do almost as good of a job for most noncritical applications.
With this guide, you should be able to generate almost any electronic signal you’ll ever need, without having to spend a bundle.
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