In mixed-signal embedded hardware design, passive RC filters are ubiquitous. Whether you are implementing a Low-Pass filter for ADC anti-aliasing, a High-Pass filter for DC-blocking, or cascading stages for higher-order roll-offs, understanding the exact frequency response is critical.

Filter Analysis vs. Synthesis

Calculating $f_c = 1 / (2\pi RC)$ is straightforward for a single stage. However, when cascading passive stages to create a 2nd Order filter (or a Band-Pass filter), you introduce a loading effect. The second stage draws current from the first, shifting the true cutoff frequencies and introducing an insertion loss.

Use the advanced tool below in Analysis Mode to plot the exact response of a complex circuit, or use Synthesis Mode to enter your desired Frequency (Hz, kHz, MHz, GHz) and instantly calculate the required Resistor for your available Capacitors.

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