This is a high-pass filter implemented using a resistor and an inductor. The inductor passes lower frequencies, causing the voltage across it to be reduced and keeping the output voltage closer to ground. The inductor blocks higher frequencies, causing reduced current across the resistor and keeping the output voltage closer to the input voltage.
Below the circuit is the frequency response in dB for a range of frequencies. You can click on the frequency response graph to see the circuit in operation at that particular frequency.
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Analog Filter Applet