Electronic – input capacitance of pins in IC and what effect does it have

buffercapacitanceintegrated-circuit

What is the purpose and the definition of the input capacitance parameter in the datasheet.

I have tried to research about this topic but was only able to find the input capacitance parameter with respect to operational amplifiers only. Even after those research, I was not able to understand the concept of input capacitance with respect to this buffer IC.

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Can someone help me with my following queries :

  1. What is the definition of input capacitance of a pin in an IC?
  2. How is it measured in the first place and is it applicable to all pins in the IC? I am sure, different pins of the IC must have different circuits connected inside. So, the input capacitance of those pins might be different.

  3. Is the input capacitance parameter relevant only to supply/signal pins?

  4. Why should we care about this parameter of the IC while we design our circuit and how is it relevant?

Best Answer

1) What is the definition of input capacitance of a pin in an IC?

It's the capacitance from that pin to ground or 0 volts.

2) How is it measured in the first place and is it applicable to all Pins in the IC?

It's probably not measured on production items; rather it is essentially always that value unless there is a significant production anomaly on the die. It's applicable to signal inputs.

3) And Why should we care about this parameter of the IC while we design our circuit and how is relevant?

It's a very relevant parameter given that a signal with significant source resistance will have difficulty keeping its rise and fall times short/fast with too much input capacitance.

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