[SOLVED] Pin capacitance importance

Hi All,

Why does a pin of an IC have a capacitance associated with it?

What is its importance?

I have not been able to get a clear picture of it. Please help.

Naveen

They have capacitance because they are conductors separated by an insulator. they also have inductance.

Both of those have an impact on high frequency design.

See here:

**broken link removed**

Thanks FoxyRick.

One more question I have.
What does the capacitance and resistance of the oscilloscope probe mean?

Just what it says - your 'scope probe (and the 'scope itself) has a resistance and a capacitance. These might be important if the circuit you are measuring will be influenced by the load the probe puts on it. For instance, a very high impedance circuit (like 10's of MΩ) will definitely be loaded and therefore altered by a normal probe. So you won't get a true reading of the circuit.

The oscilloscope itself has a standardised 1MΩ in parallel with 20pF across the input.

x1 and x10 probes are common. The x1 probe is basically just a wire. The x10 probe has a series 9MΩ resistor in probe, and a frequency compensation capacitor of 2.2pF variable. So, the 'scope and probe together form a 1:10 divider while increasing the input impedance of the probe.

Other x10 (and higher) schemes are possible, but the principle is the same.

There's a good document here:

**broken link removed**

Thanks a lot for the explanation and link. The pdf link was very useful.