Capacitors connected to both positive rail and ground!

Thread Starter

PauloConstantino

Joined Jun 23, 2016
266
I am trying to work out what is the equivalent capacitor to ground, of two capacitors connected to the positive and ground rails. Here's a diagram.

How can I substitute the capacitor connected to Vdd into another one connected to ground?

 

kubeek

Joined Sep 20, 2005
5,682
If your voltge source is an ideal one, then it doesn´t matter if the cap is connected to ground or +5V, so you can connect both in parallel to ground.

Nevertheless, what is it that you are trying to achieve?
 

Thread Starter

PauloConstantino

Joined Jun 23, 2016
266
If your voltge source is an ideal one, then it doesn´t matter if the cap is connected to ground or +5V, so you can connect both in parallel to ground.

Nevertheless, what is it that you are trying to achieve?

Why doesnt it matter? (I am working on some problems for my university course)
 

WBahn

Joined Mar 31, 2012
25,249
If your voltge source is an ideal one, then it doesn´t matter if the cap is connected to ground or +5V, so you can connect both in parallel to ground.

Nevertheless, what is it that you are trying to achieve?
I think you are thinking from a small signal standpoint. It looks like the TS is asking about large scale.

Though, depending on what the TS is looking at, a small-signal standpoint might be appropriate, so your question is very apropos.
 

kubeek

Joined Sep 20, 2005
5,682
For AC analysis of linear circuits, DC voltage sources are considered a short and DC current sources an open circuit.
You can look at it like this, since an ideal voltage source is rock stable and wont change the voltage in any way, you can wiew it as being the same as ground, just with a little offset. And since the offset voltage doesn´t matter for AC analysis, a cap to DC supply is equivalent to a cap to ground.
 

Thread Starter

PauloConstantino

Joined Jun 23, 2016
266
I forgot to say that I am looking only at the transients and not the steady state. I am looking at the delay caused by the two capacitors and I'd like to know the difference between the two. Is there any difference only because they are connected to Vdd and GND ?
 
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