SAWTOOTH WAVES

Some ac waves reverse their polarity at constant but not instantaneous rates. The slope of the amplitude-versus-time line indicates how fast the magnitude is changing. Such waves are called sawtooth waves because of their appearance.
In Fig. 1, one form of sawtooth wave is shown. The positive-going slope (rise) is extremely steep, as with a square wave, but the negative-

Fig. 1. A fast-rise, slow-decay sawtooth wave.

going slope (fall or decay) is gradual. The period of the wave is the time between points at identical positions on two successive pulses. Another form of sawtooth wave is just the opposite, with a gradual positive-going slope and a vertical negative-going transition. This type of wave is sometimes called a ramp (Fig. 2). This waveform is used for scanning in cathode-ray-tube (CRT) television sets and oscilloscopes. Sawtooth waves can have rise and decay slopes in an infinite number of different combinations. One example is shown in Fig. 3. In this case, the positive-going slope is the same as the negative-going slope. This is a triangular wave.

Fig. 2. A slow-rise, fast-decay sawtooth wave, also called a ramp wave.

Fig. 3. A triangular wave.