Hints and Tips - Considering bandwidth when choosing an oscilloscope.
For digital signals, scopes must capture the fundamental, third and fifth harmonics otherwise the display will lose key features which may be crucial to the end user. Therefore the bandwidth of the scope together with the probe should similarly be at least 5x the maximum signal bandwidth for better than ±2% measurement error –This is sometimes called the ‘five times rule’. This is also needed for accurate amplitude measurements. High-speed digital, serial communications, video and other complex signals for example can therefore require scope bandwidths of 500 MHz or more.
When selecting bandwidth, use the ‘five times rule’. If bandwidth is too low, your oscilloscope will not resolve high-frequency changes. Amplitude will be distorted. Edges will vanish, details will be lost.