These generators are often employed with an oscilloscope as the measuring devices.The waveforms displayed by the oscilloscope either at the output or at pertinent points in the system under test provide qualitative as well as quantitative information about the system or device under test.
These generators are designed for generating a periodic train of equal-amplitude pulses,as shown in fig.In pulse generators,the duration of the on time of a pulse may be independent of the time between pulses.However, if the pulse train has the property of being "on" 50 per cent ,the waveforms is called the square wave and the generators producing such waveform are called the square-wave generators.Thus square-wave generators can be considered to be a special class of pulse generators.
square-wave generators are used for investigating the low frequency characteristics of a system including testing of audio systems.Square waves are also preferred over short-duration pulses if the transient response of a system needs a comparatively high settling time.
Pulse generators are designed to generate pulses as close to ideal pulses as possible.High-quality pulses ensure that any distortion in the output pulse from a test circuit is owing to test circuit alone.The amplitude,pulse width,and period of the generated pulses are usually adjustable over various ranges.The duty cycle is also made adjustable;but in case the power contained by each pulse is large,the maximum duty cycle must be kept small.As the maximum duty cycle of a pulse generator is reached,the waveform of the pulse become irregular or the pulse width no longer increases.
The output impedance of the pulse generator is an important consideration in fast pulse systems.This is so because the generator,which has a square impedance matched to the connecting cable,will absorb reflections resulting from impedance mismatches in the external circuitry.If it is not so,total absorption would not take place,a portion of the pulse would be re- reflected,and spurious pulses would appear to be generated from the pulse generator.
DC coupling of the output circuit is necessary when retention of the dc bias levels in the test circuit s desirable,inspite of variations in pulse width,pulse amplitude, or pulse repetition rate (PRR).
Nice
ReplyDelete