Tektronix P6330 Reference

P6330 3.5 GHz Differential Probe Instruction Manual 19

Reference

This section contains important reference informat ion about

differential measurements and how to increase the accuracy of your

measurements.

Whilesuitableinmanyapplications,single-ended measurementscan

present problems in the following situations:

HWhen the signal is not referenced to earth ground

HWhen the signal being measured is distorted or changed by

connecting or disconnecting the probe ground reference lead

Devices designed to make differential measurements avoid the

problems posed by single-ended systems. These devices include a

varietyofdifferentialprobes, differentialamplifiers,andisolators.

The differential amplifier (Figure 9) is at the heart of any device or

system designed t o make differential measurement s. Ideally, the

differential amplifier rejects any voltage tha t isc ommon to the inputs

and amplifies any difference between the inputs. Voltage that is

common to both inputs is often referred to as the Common-Mode

Voltage(VCM) and voltage that is different as the Differential-Mode

Voltage(VDM).