Electrical & Computer
Bode Filter Lab
A static textbook Bode plot can't show you how the response moves. Pick a low- or high-pass RC filter, drag the resistor and capacitor, and the magnitude (dB) and phase curves redraw live over a log-frequency axis. The corner sits at fc = 1/(2πRC); above it a low-pass rolls off at 20 dB per decade while the phase slides toward −90°. It connects component values to the frequency response the way equations alone never quite do.
995 Hz
Cutoff fc
-3 dB
At fc
20 dB/dec
Roll-off
The method, with your numbers
First-order RC frequency response
- 1
Find the corner (−3 dB) frequency
fc = 1 / (2πRC)
fc = 1 / (2π · 1000 Ω · 160 nF) = 994.72 Hz
Only the product RC matters — halve R and double C and the corner doesn't move.
- 2
Gain at the corner
gain(f) = 20·log₁₀( 1 / √(1 + (f/fc)²) )
gain(fc) = 20·log₁₀(1/√(1 + 1²)) = -3.01 dB
−3 dB means half the output POWER gets through — that's the definition of cutoff, not where the signal stops.
- 3
Phase at the corner
φ(f) = −tan⁻¹(f/fc)
φ(fc) = −tan⁻¹(1) = -45°
The output lags the input: 0° far below fc, exactly −45° at fc, sliding toward −90° far above.
- 4
Roll-off one decade above the corner
gain(10·fc) = 20·log₁₀( 1 / √(1 + 10²) )
gain(9.95 kHz) = -20.04 dB
First-order slope: every decade of frequency costs ≈20 dB. Drag R or C — the corner slides but the slope never changes.
Drag any control above — every number here recalculates. Want this method for any problem? Step Sheets →
Filter
The corner sits at fc = 1/(2πRC) — halve R or C and it doubles. Below fc a low-pass passes; above, it rolls off at 20 dB per decade with the phase sliding to −90°.
How to use this simulation
A static textbook Bode plot can't show you how the response moves. Pick a low- or high-pass RC filter, drag the resistor and capacitor, and the magnitude (dB) and phase curves redraw live over a log-frequency axis. The corner sits at fc = 1/(2πRC); above it a low-pass rolls off at 20 dB per decade while the phase slides toward −90°. It connects component values to the frequency response the way equations alone never quite do.
Everything runs in your browser — no sign-up, no download. Change a value and the result updates instantly, so you can build a feel for how each input shapes the outcome. It pairs with Crameleon's practice exams and step sheets when you want to go from intuition to working the problems.