High and Low Pass Filters

by Paul Safara

Submitted : Spring 2012

The purpose of this project is to show how an RC circuit can be used as a low and high pass filter. By examining the properties of an incoming audio signal and the circuit it is going into we were able to find out how the specified circuit affects the signal. By integrating a differential equation that illustrates the behavior of the capacitor voltage and substituting the values for Ohms, Farads, frequencies of the audio signal, and time for their specified variables in the equation we were able to find out what the capacitor voltage would be at each interval of .01 seconds. We then also figured out the behavior of the resistor voltage and audio signal would be by using each governed equation and substituting values like we did in the differential equation for the capacitor voltage. We then made a graph that illustrated the behavior of the capacitor, resistor, both frequencies of the incoming signal independently, and the  signals combined. When we compared these graphs to each other it was clear that the resistor and the capacitor were splitting up the frequencies of the incoming signal in their own way.

The graph for the resistor correlated to the graph of the higher frequency of the audio signal and the graph for the capacitor correlated to the graph of the lower frequency of the audio signal. This shows us that the resistor was acting as a high pass and the capacitor was acting as a low pass.

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