Pulse generators are electrical test equipment used to generate pulses that are injected into devices under test in order to study the behavior of these devices. Basic pulse generators allow users to control:

• the frequency or pulse repetition rate
• the pulse width
• the pulse high-voltage and pulse low-voltage levels
• a delay for an internal or external trigger

More complex products allow control over the rise time and fall time of the pulses. To form outputs, pulse generators may use analog techniques, digital techniques, or both. For example, analog circuitry may be used to control parameters such as pulse amplitude, rise time, and fall time. Digital controls can be used to determine the pulse repetition rate and duration.

Specifications

Selecting pulse generators requires an understanding of product specifications and parameters. Pulse repetition rate or frequency is the average number of pulses per unit of time during a specified period. Pulse width or pulse length is the interval between the first and last instances that instantaneous amplitude reaches a specified fraction of peak pulse amplitude. Pulse generator high-voltage and pulse generator low-voltage are, respectively, the highest and lowest voltages that products can produce. Rise time is the elapsed time for an output to rise from low levels due to peak value. Conversely, fall-time is a measurement of how long it takes for a pulse’s trailing edge to fall from a higher reference value to a lower reference value of amplitude. When selecting pulse generators, delays for internal triggers and external triggers are also important specifications to consider.

Applications

Pulse generators differ in terms of applications and approvals. Although most products are voltage sources, current pulse generators are also available. In addition to injecting pulses into the device under test, pulse generators that also function as digital delay generators can be used as a stimulus or clock signal. For example, pulse generators that work as digital delay generators can be used to drive lasers, modulators, or optical components. Pulse generator outputs can also produce the modulation signal for a signal generator, an electronic device that generates repeating electronic signals in either analog or digital form.

Standards

In terms of approvals, pulse generators may bear approval marks from Underwriters Laboratories (UL) or the Canadian Standards Association (CSA).

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Image credit:

National Instruments