Electrical – Bode Phase Plot of RC High-Pass Filter

bode plotfilterhigh pass filterphase

I have been trying to understand Bode Phase Plot of RC High pass filter.

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I know that from my engineering that voltage lags behind the current passing through the capacitor. So, I assume the current through capacitor will be in-phase with the input voltage waveform and that same current will pass through the resistor. So, output voltage should be in-phase with input waveform.

Can someone explain me the Bode phase plot of the filter when frequency is swept from zero to cut-off frequency via time domain analysis?

enter image description here

Best Answer

Note that current is actually common to both C and R, not really as shown in the schematic.

If you compare the input voltage (Vin) with the output voltage (Vout), the input amplitude is always >= output amplitude. At low frequencies, output is much smaller than input.
And at low frequencies, phase of Vout leads phase of Vin:
at frequency below cutoff (in stop-band)
At high frequency, well into the passband, Vout amplitude is nearly equal Vin amplitude, and phase of Vout approaches that of Vin:
at frequencies above cutoff (in pass-band)


vectors of circuit voltages