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This page is used to design filters with 1. order filter cutoff. Many different combinations of resistors, capacitors and inductors are supported.

No series/parallel resistors | A resistor in series with the active element | A resistor parallel with the active element | Both a series and a parallel resistor | Placement of the active element(s) |
---|---|---|---|---|

Highpass (C) | Highpass (C-Rs) | Highpass (C-Rp) | Highpass (C-Rp-Rs) | A capacitor in series with the signal |

Lowpass (C) | Lowpass (C-Rs) | Lowpass (C-Rp) | Lowpass (C-Rp-Rs) | A capacitor to ground |

Lowpass (L) | Lowpass (L-Rs) | Lowpass (L-Rp) | Lowpass (L-Rp-Rs) | A inductor in series with the signal |

Highpass (L) | Highpass (L-Rs) | Highpass (L-Rp) | Highpass (L-Rp-Rs) | A inductor to ground |

Bandpass (CLs) | Bandpass (CLs-Rs) | Bandpass (CLs-Rp) | Bandpass (CLs-Rp-Rs) | A inductor and capacitor in series with the signal |

Bandstop (CLs) | Bandstop (CLs-Rs) | Bandstop (CLs-Rp) | Bandstop (CLs-Rp-Rs) | A inductor and capacitor in series to ground |

Bandstop (CLp) | Bandstop (CLp-Rs) | Bandstop (CLp-Rp) | Bandstop (CLp-Rp-Rs) | A inductor and capacitor in parallel and in series with the signal |

Bandpass (CLp) | Bandpass (CLp-Rs) | Bandpass (CLp-Rp) | Bandpass (CLp-Rp-Rs) | A inductor and capacitor in parallel and connected to ground |

C | The capacitor value |

L | The inductor value |

Rl | The DC resistance of the inductor |

Rs | An external resistor in series with the C and/or L |

Rp | An external resistor parallel with C and or L |

R | The resistor, this can be the load impedance for some filter configurations |

Curve plot | Show a curve of the filters frequency responce (Select the "out" node) |

Waveforms | Connect to the waveforms page and make it possible to see what the filter does to an actual waveform |

Input/Output | Add some components to the input/output of the filter |

Fo | Center/cutoff frequency of the filter |

F1 ... F2 | Frequency range for a bandpass/bandstop filter. |

Passband loss | Loss in the pass band, the value is in dB |

Stopband loss | Loss in the stop band, the value is in dB |

"Slider" | The slider is used to select the bandwith of bandpass/bandstop filters |

Limit | Defines the level for the cutoff frequency, usual 3 dB |

Freq n | A list of frequencys, a signal analysis is done at each of these frequency. It is possible to write DC for a DC analysis |

R | The resistor in the filter |

C | The capacitor in the filter |

L | The inductor in the filter |

Rs | A resistor in series with the active element |

Rp | A resistor in parallel with the active element |

Fo | Center/cutoff frequency of the filter |

F1 ... F2 | Range for a bandpass/bandstop filter |

Passband gain | Gain in the passband |

Stopband gain | Gain in the stopband |

Zin min | The minimum Zin value |

Zin max | The maximum Zin value |

Zout min | The minimum Zout value |

Zout max | The maximum Zout value |

Bandwidth: Passband gain | Passband gain for a bandpass/bandstop filter |

Bandwidth: xx dB low freq | The low frequency where the output is "Limit" dB below (Limit is from configuration page and is usual 3 dB) |

Bandwidth: xx dB high freq | The high frequency where the output is "Limit" dB below |

Bandwidth: xx dB bandwidth freq | The range between the above tow frequencys |

Small signal analyses: At | Frequency for this analysis, see config page |

Small signal analyses: Gain | Gain at this frequency |

Small signal analyses: Phase | Phase at this frequency |

Small signal analyses: Zin | Input impedance at this frequency |

Small signal analyses: Zout | Output impedance at this frequency |

- Use the input/output networks to simulate "real life" input and output impedances
- When using "Curve plot" it is possible to click on the curve to measure values
- To enter values as a factor and not in dB use the function todB, i.e. to enter a value of 10 times in the stopband loss field use "todB(10)"

- For selecting component standard values, use the Prefered components page.
- For only calculating Fo use Fo page.
- For calculation impedance of a capacitors/inductors use Ohms law page.
- For designing inductors use Air coil page.
- For designing non-standard component values use Series/Parallel page.
- For dB conversion use dB page.

```
FilterLP1(f0,f)
FilterHP1(f0,f)
FilterLP1cpx(f0,f)
FilterHP1cpx(f0,f)
RIAA(freq)
RIAAIEC(freq)
RIAAcpx(freq)
RIAAIECcpx(freq)
```

They can be used to generate curves or tables with, for more documentation see the Calculator page.

The following functions can be usefull on this page:

```
todB(times)
todBpwr(timesPower)
```