Overcompensated oscilloscope probe

Right, good practical example!

Thanks!

Excuse my ignorance, I can see that the11.1pF does give a proper square wave, but what is the significance of this.

Billy you are right, this is missing in the description. The problem is the following. You have a scope with some input impedance. Most common is 1MOhm without an extra probe. In case you use a 10:1 10MOhm probe (which is actually just 9MOhm) you get beside the resistance a parasitic capacitance with the probe. If this capacitance does not match the fix input capacitance, your measurements will be wrong. See topic capacitive voltage divider. Almost all scopes do have a little rectangular generator to the external use (a little blank connector pad at front) frequency is low around 1kHz, were you can connect your probe before you use it, and you can align with a screw driver the probe capacity. So even a low probe capacity might be bad if the scope input capacity is high. And sure a high probe capacity is bad if the input capacity is low. So time constant of Input and probe have to be identical for best results. 9*11.1 = 1*100

@hurz thanks for the explanation.