Specifications

17
Important Oscilloscope Performance Properties
Bandwidth and channels
Many oscilloscope properties
dramatically affect the
instrument’s performance and,
in turn, your ability to accurately
test devices. This section covers
the most fundamental of these
properties. It also will familiarize
you with oscilloscope terminology
and describe how to make an
informed decision about which
oscilloscope will best suit your
needs.
Bandwidth
Bandwidth is the single most
important characteristic of an
oscilloscope, as it gives you an
indication of its range in the
frequency domain. In other
words, it dictates the range of
signals (in terms of frequency)
that you are able to accurately
display and test. Bandwidth
is measured in Hertz. Without
sufficient bandwidth, your
oscilloscope will not display an
accurate representation of the
actual signal. For example, the
amplitude of the signal may be
incorrect, edges may not be clean,
and waveform details may be lost.
The bandwidth of an oscilloscope
is the lowest frequency at which
an input signal is attenuated by
3 dB. Another way to look at
bandwidth: If you input a pure
sine wave into the oscilloscope,
the bandwidth will be the
minimum frequency where the
displayed amplitude is 70.7% of
the actual signal amplitude.
For details about oscilloscope
bandwidth, see Application note
1588, Choosing an Oscilloscope
with the Right Bandwidth for
Your Application.
Channels
A channel refers to an
independent input to the
oscilloscope. The number of
oscilloscope channels varies
between two and twenty. Most
commonly, they have two or four
channels. The type of signal a
channel carries also varies. Some
oscilloscopes have purely analog
channels (these instruments
are called DSOs – digital signal
oscilloscopes). Others, called
mixed-signal oscilloscopes
(MSOs), have a mixture of
analog and digital channels. For
example, the Agilent InfiniiVision
6000 Series MSOs are available
with twenty channels, where
sixteen of them are digital and
four are analog.
Ensuring that you have enough
channels for your applications
is essential. If you have two
channels, but you need to display
four signals simultaneously, then
you obviously have a problem.
Figure 25. Analog and digital channels on an Agilent MSO 8000
Series oscilloscope
4 analog channels
16 digital channels
Oscilloscope Fundamentals