Sallen-Key High-Pass Filter Designer
Single op-amp second-order Sallen-Key high-pass: given cutoff and Q, derive standard C/R values, verify the real parameters and plot the response.
Key points
Sallen-Key High-Pass Filter Designer: Single op-amp second-order Sallen-Key high-pass: given cutoff and Q, derive standard C/R values, verify the real parameters and plot the response. Formula: f_c = 1/(2πC√(R1·R2)) ｜ Q = ½·√(R2/R1) with C1 = C2 = C. Enter parameters on the DD-CAT IDE online tool page to get results instantly, with a calculation-model diagram that updates with the inputs. With C1 = C2, Q depends only on R2/R1; high-pass stages are sensitive to input bias current, so keep R1 moderate.
Inputs
f_c = 1/(2πC√(R1·R2)) ｜ Q = ½·√(R2/R1) with C1 = C2 = CCalculation model (updates with parameters)
Bode plot (magnitude / phase, updates with parameters)
| C1 = C2 | 100 nF | |
| R1 (+ input to ground) | 7.87 kΩ | |
| R2 (feedback to + input) | 31.6 kΩ | |
| Actual cut-off f_c | 100.9 Hz | target 100 Hz，偏差 0.92% |
| Actual Q | 1.002 | target 1.000 |
| Peaking | +1.26 dB | |
| Minimum op-amp GBW | 10.11 kHz | |
| R2/R1 ratio | 4.02 | Equals 4Q² — the higher Q, the more the ratio matters |
Engineering notes
- With C1 = C2, Q depends only on R2/R1; high-pass stages are sensitive to input bias current, so keep R1 moderate.
FAQ
- What is Sallen-Key High-Pass Filter Designer for?
- Single op-amp second-order Sallen-Key high-pass: given cutoff and Q, derive standard C/R values, verify the real parameters and plot the response.
- What is the formula for Sallen-Key High-Pass Filter Designer?
- Core formula: f_c = 1/(2πC√(R1·R2)) ｜ Q = ½·√(R2/R1) with C1 = C2 = C. The tool returns results instantly using this formula and the selected parameters.
- What engineering notes should I keep in mind when using Sallen-Key High-Pass Filter Designer?
- With C1 = C2, Q depends only on R2/R1; high-pass stages are sensitive to input bias current, so keep R1 moderate.