MiscEl: 1. order filters

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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.

Configurations supported

No series/parallel resistorsA resistor in series with the active elementA resistor parallel with the active elementBoth a series and a parallel resistorPlacement 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


Input values

CThe capacitor value
LThe inductor value
RlThe DC resistance of the inductor
RsAn external resistor in series with the C and/or L
RpAn external resistor parallel with C and or L
RThe resistor, this can be the load impedance for some filter configurations
Curve plotShow a curve of the filters frequency responce (Select the "out" node)
WaveformsConnect to the waveforms page and make it possible to see what the filter does to an actual waveform
Input/OutputAdd some components to the input/output of the filter
FoCenter/cutoff frequency of the filter
F1 ... F2Frequency range for a bandpass/bandstop filter.
Passband lossLoss in the pass band, the value is in dB
Stopband lossLoss in the stop band, the value is in dB
"Slider"The slider is used to select the bandwith of bandpass/bandstop filters
LimitDefines the level for the cutoff frequency, usual 3 dB
Freq nA list of frequencys, a signal analysis is done at each of these frequency. It is possible to write DC for a DC analysis

Output values

RThe resistor in the filter
CThe capacitor in the filter
LThe inductor in the filter
RsA resistor in series with the active element
RpA resistor in parallel with the active element
FoCenter/cutoff frequency of the filter
F1 ... F2Range for a bandpass/bandstop filter
Passband gainGain in the passband
Stopband gainGain in the stopband
Zin minThe minimum Zin value
Zin maxThe maximum Zin value
Zout minThe minimum Zout value
Zout maxThe maximum Zout value
Bandwidth: Passband gainPassband gain for a bandpass/bandstop filter
Bandwidth: xx dB low freqThe low frequency where the output is "Limit" dB below (Limit is from configuration page and is usual 3 dB)
Bandwidth: xx dB high freqThe high frequency where the output is "Limit" dB below
Bandwidth: xx dB bandwidth freqThe range between the above tow frequencys
Small signal analyses: AtFrequency for this analysis, see config page
Small signal analyses: GainGain at this frequency
Small signal analyses: PhasePhase at this frequency
Small signal analyses: ZinInput impedance at this frequency
Small signal analyses: ZoutOutput impedance at this frequency

Hints


Other pages

Calculator functions

Some filter calculations can be done with functions in the Calculator. The following functions are supported:
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)