Parallel RC network

Thread Starter

skyjeff185

Joined Jan 27, 2007
13
Hi,
I am not too sure the use of parallel RC network. From a website, it just says make the signal more clear, but in what way? Thanks.
 

Dave

Joined Nov 17, 2003
6,970
Can you provide a link to the site which states this? I'm thinking a simple RC filter, but it would be useful to see it in context.

Dave
 

DrNick

Joined Dec 13, 2006
110
RC networks can be used as low or high pass filters. At high frequencies (MHz or GHz) they can be used as resonators as well.
 

Dave

Joined Nov 17, 2003
6,970
wikipedia... search RC netowrk
Where in the Wikipedia article does it say it makes the signal clearer? I suspect that you are refering to the use of the RC circuit as a simple filter - in fact its not strictly a parallel arrangement.

If you want to see more about how how RC circuits are used in filters see Volume II - Chapter 8 for some practical examples with explanations.

Dave
 

Thread Starter

skyjeff185

Joined Jan 27, 2007
13
yes thanks for the info on filters. But in particular, I'm looking at this:


Anyone knows the purpose of this. From what I know, it's not a LPF, HPF, BSF, or BPF. Thanks!
 

lattesurf

Joined Mar 6, 2007
9
yes thanks for the info on filters. But in particular, I'm looking at this:


Anyone knows the purpose of this. From what I know, it's not a LPF, HPF, BSF, or BPF. Thanks!
I'm guessing that it is there for completeness. The capacitor would attempt to reduce any voltage ripples from Vin. This would give the "clearer signal" that you mentioned earlier on.

The description where you linked the image from describes that the capacitor current is 90degress out of phase with Ir & Is. So perhaps the resistor is there to demonstrate the out of phase difference.
 

Ron H

Joined Apr 14, 2005
7,014
I'm guessing that it is there for completeness. The capacitor would attempt to reduce any voltage ripples from Vin. This would give the "clearer signal" that you mentioned earlier on.

The description where you linked the image from describes that the capacitor current is 90degress out of phase with Ir & Is. So perhaps the resistor is there to demonstrate the out of phase difference.
That's a pretty stupid schematic. Vin and Vout are identical!
A parallel RC network can be part of a lowpass or highpass or allpass filter, depending on the other components in the network.
 

lattesurf

Joined Mar 6, 2007
9
That's a pretty stupid schematic. Vin and Vout are identical!
A parallel RC network can be part of a lowpass or highpass or allpass filter, depending on the other components in the network.
As described in the decription of the parallel RC schematic from wikipedia http://en.wikipedia.org/wiki/RC_filter
It does state that Vout and Vin is the same. In my opinion, the resistor is there to demonstrate that the current is 90degress out of phase in the capacitor to the current in the resistor/source.

It serves no purpose by its own configuration alone, unless you just want to delay the capacitor's current by 90degrees.
 

thingmaker3

Joined May 16, 2005
5,084
Not always 90 degrees to the source...

For current phase angle, take the inverse tangent of the product of capacitor current over resistor current.
 
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