times). The lowfrequency response affects any waveform when the
voltage is constant (pulse duration), or when the voltage change is
gradual as in the rise of a sawtooth waveform.
b. These principles may be used, for example, to determine the
The voltage of this waveform changes gradually during the rise time
until the maximum amplitude is reached, and then fails sharply to
zero during the decay time. In Figure 8B, a poor lowfrequency
response causes the omission of the first, second, and third
harmonics in the rising portion of the wave. In Figure 8C, a poor
highfrequency response causes the voltage to decay more gradually
and run into the rise time of the next cycle.
Figure 8. Sawtooth wave frequency response
c. The bandwidth of a circuit must be low enough to pass the
fundamental frequency, and sufficiently high to pass a frequency of
1/2tf. Consider the bandwidth required to pass a sawtooth voltage
with a fundamental frequency of 1000 Hz, and a decay time (tf) of 5
usec. The lowfrequency response limit of the circuit must be 1 kHz,
and the highfrequency response must be 1/2tf or 1/10 x 106 or 100
kHz. For good reproduction of the waveform, the bandwidth of the
circuit must be 99 kHz (1 kHz to 100 kHz).
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