How to graph amplitude vs. frequency for a Low-Pass Filter?

In summary, the conversation discusses the process of graphing the theoretical amplitude of the output from a low-pass filter versus frequency for a lab class. The equation Vout = Vin*(Rc/sqrt(R^2 + Rc^2) is mentioned, but the meaning of ε is unclear. After some research, the equation 1/sqrt(1+(2πfRC)^2) is suggested, but it results in a straight line. The correct equation for capacitive reactance is Xc = 1/(2πfC).
  • #1
eroc1002
1
0

Homework Statement


For my lab class my professor wants us to graph the theoretical amplitude of the output from a low-pass filter vs. frequency. I have the resistance and capacitance that I chose for the RC circuit and a V(in). Is there an equation that I should be able to use to relate these and produce a graph?

Homework Equations


In my notes I have an equation Vout = Vin*(Rc/sqrt(R^2 + Rc^2) and Rc = 2πfε but I have no idea what epsilon represents because I forgot to ask my professor when I was taking the notes.

3. Attempt at a solution
After doing some research, I tried to use 1/sqrt(1+(2πfRC)^2)to get a ratio of Vo/Vin but all I got was a straight line.
 
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  • #2
I think the epsilon should be C and RC is the capacitive reactance 2πfC.

As to why you got a straight line, it probably has to do with not plotting in the correct frequency range.
 
  • #3
eroc1002 said:
In my notes I have an equation Vout = Vin*(Rc/sqrt(R^2 + Rc^2) and Rc = 2πfε
First, don't use "Rc" for capacitive reactance. Use Xc. "R" is always resistance in this context.
Second, capacitive reactance is not 2πfC. It's the inverse.
 
  • #4
rude man said:
... capacitive reactance is not 2πfC. It's the inverse.
Right you are. I missed that. :oops:
 

1. What is a low-pass filter?

A low-pass filter is an electronic circuit that allows low-frequency signals to pass through while attenuating or blocking high-frequency signals.

2. How do I graph amplitude vs. frequency for a low-pass filter?

To graph amplitude vs. frequency for a low-pass filter, you will need to measure the amplitude of the output signal at different frequencies. Then, plot these values on a graph with frequency on the x-axis and amplitude on the y-axis. This will show you the amplitude response of the low-pass filter at different frequencies.

3. Can I use any type of graph to plot amplitude vs. frequency for a low-pass filter?

Yes, you can use any type of graph to plot amplitude vs. frequency for a low-pass filter. However, a common choice is a logarithmic scale for the frequency axis, as this better represents the wide range of frequencies typically used in low-pass filters.

4. How does the cutoff frequency affect the graph of amplitude vs. frequency for a low-pass filter?

The cutoff frequency is the frequency at which the amplitude of the output signal is reduced by half (-3dB) compared to the input signal. As the cutoff frequency decreases, the low-pass filter will attenuate higher frequencies more, resulting in a steeper drop in the amplitude vs. frequency graph.

5. What factors can affect the shape and slope of the amplitude vs. frequency graph for a low-pass filter?

The shape and slope of the amplitude vs. frequency graph for a low-pass filter can be affected by the components used in the circuit, such as the type and value of resistors and capacitors. Additionally, the design and configuration of the filter can also impact the graph, such as the order of the filter and the type of filter (e.g. Butterworth, Chebyshev, Bessel).

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