Differential Mode And Common Mode; Differential Mode Range And Common Mode Range; Differential Input Impedance - Teledyne Lecroy HVD3102 Operator's Manual

HVD3102 and HVD3106 High-Voltage Differential Probes

Differential Mode and Common Mode

Differential probes sense the voltage difference that appears between the + and – inputs. This is
referred to as the Differential or Normal Mode voltage. The voltage component that is referenced
to earth and is identical on both inputs is rejected by the amplifier. This is referred to as the
Common Mode voltage and can be expressed as:

Differential Mode Range and Common Mode Range

Differential Mode range is the maximum signal that can be applied between the + and - inputs
without overloading the amplifier, which otherwise would result in clipping or distorting of the
waveform measured by the oscilloscope.
The Common Mode Range is the maximum voltage with respect to earth ground that can be
applied to either input. Exceeding the common mode range can result in unpredictable
measurements. Because the Common Mode signal is normally rejected, and not displayed on
the oscilloscope, the user needs to be careful to avoid accidentally exceeding the common
mode range.

Differential Input Impedance

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