Sawtooth waves
Some ac waves rise and fall in straight lines as seen on an oscilloscope screen. The slope
of the line indicates how fast the magnitude is changing. Such waves are called sawtooth
waves because of their appearance.
Sawtooth waves are generated by certain electronic test devices. These waves provide
ideal signals for control purposes. Integrated circuits can be wired so that they produce
sawtooth waves having an exact desired shape.
Fast-rise, slow-decay
In Fig. 9-3, one form of sawtooth wave is shown. The positive-going slope (rise) is extremely
steep, as with a square wave, but the negative-going slope (fall or decay) is
gradual. The period of the wave is the time between points at identical positions on two
successive pulses.
Slow-rise, fast-decay
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,
because it looks like an incline going upwards (Fig. 9-4). This waveshape is useful for
scanning in television sets and oscilloscopes. It tells the electron beam to move, or
trace, at a constant speed from left to right during the upwards sloping part of the wave.
Then it retraces, or brings the electron beam back, at a high speed for the next trace.
Variable rise and decay
You can probably guess that sawtooth waves can have rise and decay slopes in an infinite
number of different combinations. One example is shown in Fig. 9-5. In this case, the
positive-going slope is the same as the negative-going slope. This is a triangular wave.
