Start your work defining desired filter parameters on Wizard tab, then do an initial calculation of filter components. Schematic tab shows the filter schematic, all components have exact values. Charts tab shows the filter functions and Data tab shows the numeric values.
The next step is tuning the component values. Schematic tab allows to tune the resistor and capacitor values based on the standard series. Charts tab allows to see selected frequency range precisely and recalculate values within a desired range.
After the filter tuning the result can be saved as a picture, a CSV-file, an html-file report or a binary file, if you need to continue the work lately.
The program uses the classical approach, the stages are arranged with the lowest Q near the input and the highest Q near the output. However it make sense to move the first-order stage at the end of the circuit to reduce the filter noise. Refusing of an IC and using a passive output filter will reduce the noise even more if higher output impedance is allowed. The cumulative noise at 10kHz could be reduced for about 25% for a 5-th order 1kHz LPF if it uses ICs with 7 nV/sqrt(Hz) noise density. This configuration can also avoid peaking due to high Q sections.
Wizard contains four areas:
The specifications for the filter are:
The program offers the responses:
The program offers the topologies:
The program also offers the next topologies for 2-nd order Lowpass Filter:
Design of Multiple-Feedback Differential Input topology is equal to Multiple-Feedback Fully Differential topology, so the program doesn't suggest that topology.
Filters with "In-The-Loop" topology are affected by load impedance. The load impedance is considered high for their calculations.
Bandpass and Bandstop filters with Sallen-Key topology are not allow to tune gain and Q independently, so the result will not fully match the specified parameters.
After the initial calculation, the filter components have calculated values.
The "Component Values" table shows the calculated values,
the closest standard value according to the selected standard values, and the used value.
The "Gain components" table, together with the fields "Accuracy" and "Zin",
allows to find precisely the values of the components, which determines the gain of the cascade.
Resistance is entered in Ohms, сapacitance is entered in pF.
"Zin" - resistance or capacitance of an element of the first table column.
"Reset" button - sets the values of the components in accordance with the selected standard values.
The program is trying to find the most appropriate values to specified parameters wherever it is possible.
For a filter with multi-loop feedback and differential input the table "Gain components"
offers the values to get the equal impedance at both inputs.
The field "Zin" has the desired input impedance.
The table has only the values that have the desired gain and the input impedance tolerance better then entered accuracy.
The filter specification panel on top shows the parameters of the filter. "Number of Stages" shows only the quantity of filter stages, this number doesn't include special cascades like an adder. The "Cascade" combo box allows to get access to all the filter cascades.
The "Cascade Parameters" table shows the desired parameters of the selected cascade, the text on the circuit shows the parameters at current component values.
You can recalculate the filter functions according to the entered values after correcting the component values.
The result of the work can be saved as a picture, a list of components, a binary file, or an html-file that contains the filter parameters, schematic of each cascade, lists of the elements, the parameters of the cascades.
Viewing the frequency and the phase response, the group delay and the dependence of the input impedance on frequency.
The representation of the calculated functions in the tabular form.
Calculation of filter parameters at known values of circuit elements.
Send a message to dmilvdv@gmail.com to get a key.
A license costs 30$.
Filter Designer v6.7
email: dmilvdv@gmail.com
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