Bandwidth and Rise Time

Question:  How is bandwidth related to rise time for oscilloscopes?

Answer:  Historically, oscilloscope frequency response tended to approximately follow the rule: Bandwidth x risetime = 0.35. This corresponds to a 1- or 2-pole filter roll-off in the frequency domain. Today, at the high end, most real-time digital oscilloscopes more closely follow this rule:

Bandwidth x rise time = 0.45.

This corresponds to a much steeper frequency roll-off above the specified bandwidth. The steeper roll-off is more desirable in digital oscilloscopes that oversample by 4x, 3x, or even less because it prevents aliasing by eliminating any signal above the Nyquist frequency (1/2 the sample rate – the minimum sample rate required for accurate signal representation).

For more information on the topic of bandwidth vs. rise time check out this white paper.

Explore posts in the same categories: Ask Scope Guru Q/A, Uncategorized


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