Bode plots & margins worksheet with answers

Free printable Bode plots & margins worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
vin​R = 10 kΩC = 100 nFvout​

Find the corner (−3 dB) frequency fc of the RC low-pass filter shown, with R = 10 kΩ, C = 100 nF. Give it in Hz.

R = 10 kΩC = 100 nF
fc = Hz
2.Easy
|H| (dB)110100100010000−60−40−2002040?ω (rad/s)

Sketch the asymptotic Bode magnitude plot of G(s) = 500000/((s + 1000)(s + 10)). What is the slope n of the straight-line asymptote above 1000 rad/s, in dB/decade?

G(s) = 500000/((s + 1000)(s + 10))
n = dB/dec
3.Medium
vin​L = 1 mHC = 0.1 µFR = 10 Ωvout​

In the series RLC band-pass filter shown the output is taken across R = 10 Ω, with L = 1 mH and C = 0.1 µF. Find the −3 dB bandwidth BW in Hz.

R = 10 ΩL = 1 mHC = 0.1 µF
BW = Hz
4.Medium
vin​C = 10 nFR = 1 kΩvout​

The RC high-pass filter shown has R = 1 kΩ, C = 10 nF. A sinusoidal input of 3.2 kHz is applied. Find the gain |H| = |vout/vin| in dB.

R = 1 kΩC = 10 nFf = 3.2 kHz
|H| = dB
5.Hard
|H| (dB)0.10.1111010100100−80−60−40−2002040ω (rad/s)φ (°)ω (rad/s)−270−180−900ω180​ = ?

A unity-feedback loop has the open-loop transfer function L(s) = 8/(s(s + 2)(s + 3)). Find the phase crossover frequency ω180, where ∠L(jω) = −180°.

L(s) = 8/(s(s + 2)(s + 3))
ω180 = rad/s
6.Hard
|H| (dB)0.10.1111010100100−80−60−40−2002040ω (rad/s)φ (°)ω (rad/s)−270−180−900ω180​

A unity-feedback loop has the open-loop transfer function L(s) = 614/(s(s + 8)(s + 9)). Find the gain margin GM in dB.

L(s) = 614/(s(s + 8)(s + 9))
GM = dB

Answer key

  1. 1. fc = 159.2 Hz
  2. 2. n = −40 dB/dec
  3. 3. BW = 1592 Hz
  4. 4. |H| = −14.11 dB
  5. 5. ω180 = 2.449 rad/s
  6. 6. GM = 5.992 dB

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