How do I model stray capacitance of wires in an opamp circuit?

Thread Starter

mecrotty

Joined Sep 30, 2018
5
I have searched the internet on how to model the stray capacitance of the wires going into the input of an opamp, and I seem to get the answer that I should model the stray capacitance as a capacitor coming off the wire and going straight to ground. This answer is nice, but I would like to know why it is modeled this way and none of the sources seem to explain why they model it that way.
 

ramancini8

Joined Jul 18, 2012
473
iT IS MODELED AS A CAP TO GROUND BECAUSE THAT IS USUALLY THE SITUATION. Sometimes the stray capacitance is modeled as across a component, such as the feedback resistor, but these type of capacitances are usually very small.
 

Thread Starter

mecrotty

Joined Sep 30, 2018
5
For my circuit I have modeled the parasitic capacitance across the components such as the resistors, but I just need to include the stray capacitance from the wires going to the input of the opamp. In my situation there are a bunch of wires (about 6) bundled together, would I still model the capacitance of the wires as a capacitor going to ground?
 

MisterBill2

Joined Jan 23, 2018
6,717
If you have a wire bundle you can use caps between wires as models.
And the typical capacitance between touching wires would be about 5Pf per inch that they were touching. But there is also inductive coupling. For additional considerations reading about the physical layout considerations in switching power supplies may provide some useful insight.
 
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