1 In electronic circuits powered by direct current (DC), the voltage source is usually a battery or solar cell, which produces a constant voltage and a constant current through a conductor.
In electronic circuits or devices powered by alternating current (AC), the voltage source is usually a generator, which produces a regular output waveform, such as a sine wave.
Draw one cycle of a sine wave.
Figure 5.1 shows one cycle of a sine wave.
2 A number of electronic instruments are used in the laboratory to produce sine waves. For purposes of this discussion, the term generator means a sine wave source. These generators enable you to adjust the voltage and frequency by turning a dial or pushing a button. These instruments are called by various names, generally based on the method of producing the sine wave, or the application as a test instrument. The most popular generator at present is called a function generator. It provides a choice of functions or waveforms, including a square wave and a triangle wave. These waveforms are useful in testing certain electronic circuits.
The symbol shown in Figure 5.2 represents a generator. Note that a sine wave shown within a circle designates an AC sine wave source.