# Forum: Analog Circuits Cut off freq of RC circuit

 Author: Thomas (Guest) Posted on: 2011-05-03 18:23
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Hi folks,
I know that, in case of low pass filter, or high pass filter, the cut
off frequency is equal to 1/2*pi*RC.
So how about if I have a R and C in parallel? does it behave as a low
pass filter? does it have the same freq?

Thx,

Thomas

 Author: Ina (Guest) Posted on: 2011-05-03 18:35

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>So how about if I have a R and C in parallel? does it behave as a low
>pass filter?

Without additional series element? No. Or is the input driven by a
current source?

 Author: U. B. (pasewalker) Posted on: 2011-05-03 18:48

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The voltage at the input and the voltage at the output are equal inthis
circuit.

 Author: Thomas (Guest) Posted on: 2011-05-04 08:22
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So if the R//C does not have any influence on the frequency, how about
this circuit? How can we calculate the cut off freq of it?
Thanks

 Author: U. B. (pasewalker) Posted on: 2011-05-04 12:09

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In the last circuit both resistors must be calculated as parallel.

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