Section II. Frequency-Response Analysis and Transient Response

Timing Circuits
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the wave to be a rapid change in voltage or current, caused by

circuit components, which is followed after a certain interval by

another, similar change. This method analyzes the responses of a

circuit to a transient waveform.

Section II. FREQUENCYRESPONSE ANALYSIS AND TRANSIENT RESPONSE

FREQUENCYRESPONSE METHOD OF ANALYSIS.

a. Using the frequencyresponse method of analysis, a waveform

can be analyzed by determining the number, amplitude, frequency, and

phase of sine waves required to reproduce it. The rate at which a

waveform is repeated is known as the fundamental or firstharmonic

frequency. If a waveform is repeated 1000 times per second, the

fundamental frequency is 1000 Hz (hertz per second). The second

harmonic of this waveform has a frequency equal to twice the

fundamental frequency of 2000 Hz, and the third harmonic of this

waveform has a frequency equal to three times that of the fundamental

frequency or 3000 Hz. After the harmonic frequencies have been

determined, reactance and frequency concepts can be applied to

determine various circuit responses.

b. An important factor to consider in the frequency response

method of analysis is the number of harmonics that must be included

in forming the waveshape. A helpful rule to remember is that the

maximum number of harmonics varies inversely with the width of the

pulse being formed. Therefore, the narrower the pulse width, the

greater the number of harmonics required to produce the pulse.

TRANSIENTRESPONSE METHOD OF ANALYSIS.

a. Originally, the term transient was used to describe what

occurred during the period immediately after a piece of equipment was

turned off or on, or after some unusual disturbance occurred in the

equipment. When nonsinusoidal voltages were introduced in electronic

equipment, it was found that the methods developed to study

transients could be applied to nonsinusoidal waveforms. The meaning

of transient was then expanded to include the effects of the

nonsinusoidal waveforms. Today, a transient is considered as any

brief change in voltage in a circuit followed, after a period, by a

similar change. Transient time is the period of time during which

this change occurs. Conversely, a steady state is a period when the

output pulse does not experience a change in voltage or current.

b. The transientresponse method of waveform analysis is used to

determine the response of a circuit to a transient waveform. Since

voltages are nonsinusoidal during the transient time, the study of

transients can be considered as the study of the response of a

circuit to nonsinusoidal voltages.