Digital Signal Integrity and Bandwidth: Signal’s Risetime is Important, Period is Irrelevant

What bandwidth should your scope and scope probe have? When do you have to worry about “high frequency” effects? This is basic theory relating the time and frequency domains, but too often people quote rules of thumb that, while strictly accurate, are very misleading. Typical misleading statements are:

  • the scope’s bandwidth should be at least 5 times the frequency, so you can see a reasonable waveform
  • I only have a 1kHz (i.e. 1ms period) signal, which isn’t high frequency (certainly not RF), and an audio frequency scope is sufficient

This post is a basic illustration of the “maximum frequency” in a 1kHz signal, to help dispel some misconceptions.

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