R1 connects the input to the output. C1 connects the output to ground. Low frequencies pass through with little attenuation; higher frequencies are increasingly diverted through the capacitor.
The cutoff frequency is 1 / (2πRC). At cutoff, the output amplitude is about 70.7% of the input (−3.01 dB), and the output lags by 45°.
Increasing either resistance or capacitance lowers the cutoff. Above cutoff, the gain approaches a −20 dB per decade slope. These calculations assume ideal components, an ideal source and no output load.
Explore the chart at different frequencies, then open the circuit in CircuitSim to run an AC sweep. For a frequency-independent ratio, try the voltage divider calculator. To reduce both low and high frequencies, try the passive RC band-pass calculator.
