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# Jitter Testing of Electronic Circuits

IP.com Disclosure Number: IPCOM000109643D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 100K

IBM

## Related People

Calabrese, GM: AUTHOR

## Abstract

This article describes a circuit and procedure which can be used for injecting jitter on electrical circuits. Jitter can be described as a random variation or instability in the time of occurrence of transitions on a waveform. Since clocks serve as the fundamental reference point for many logic circuits, it is important for the clock signal to be very stable. Jitter is one way of characterizing this stability. In many logic circuit applications, the clock is generated externally and supplied as an input. The test technique described here gives a method for characterizing the sensitivity of the logic to the clock input.

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Jitter Testing of Electronic Circuits

be used for injecting jitter on electrical circuits.  Jitter can be
described as a random variation or instability in the time of
occurrence of transitions on a waveform.  Since clocks serve as the
fundamental reference point for many logic circuits, it is important
for the clock signal to be very stable.  Jitter is one way of
characterizing this stability.  In many logic circuit applications,
the clock is generated externally and supplied as an input.  The test
technique described here gives a method for characterizing the
sensitivity of the logic to the clock input.

Phase-locked loop (PLL) circuits are particularly sensitive to
jitter.  These circuits are commonly used in communications.
THEORY OF OPERATION

A common application for a comparator circuit is for the
purpose of "squaring up" distorted signals.  There are two inputs,
one is the waveform as it is received and the second is a reference
voltage.  The output of this circuit will be a "high" level if the
input waveform is greater than the voltage reference, and at a "low"
level when the input waveform is less than the reference level.
Thus, the output switches levels only when the waveform crosses
through the reference voltage level.

Consider the effect of changing the reference voltage to some
higher value, but still below the maximum amplitude of the input
signal.  T...