FilterLab Application Layout and Interface
Filter Design Aid
The Filter Design Aid tab allows the user to choose the type of filter to design. The typical response of the selected filter is displayed in Figure 1.
Figure 1: Filter Design Aid Tab
Clicking Next will navigate the user to the following page where the filter attenuations and frequencies can be modified, as shown in Figure 2.
- The passband attenuation is the largest loss in magnitude of the signal in the passband. The allowable range is -0.01 dB to -3 dB.
- The stopband attenuation is the smallest attenuation of signal strength in the stopband. The allowable range is -10 dB to -100 dB.
- The passband frequency is the starting point of the passband region. The allowable range is 0.1 Hz to 1 MHz.
- The stopband frequency is the starting point of the stopband region. The allowable range is 0.1 Hz to 1 MHz.
Figure 2: Filter Design Aid Attenuation
As shown in Figure 3, the user can change the resistor and capacitor component tolerances, power supply voltages, voltage ratio gain, and topology on the next page.
Minimizing the bill of materials will cause the filter design tool to use the same op-amp in every stage of the filter. The filter design tool will pick the op-amp with the highest gain-bandwidth product of each filter stage, and use that for every stage. Note that op-amps with higher gain-bandwidth products tend to have higher power consumption. Minimizing power consumption will allow for different op-amps in each stage, thus reducing the overall power consumption.
Figure 3: Resistor Capacitor
The final page summarizes the selections and presents the filter options, reflected in Figure 4.
While it is possible to create a filter of any order, FilterLab will only design a filter of up to 8 orders. If the requirements set by the Filter Design Aid need a higher order than 8 for a particular type, it will not show up in the results. For example, if the design requirements necessitate a 10th-order Butterworth filter, a 10th-order Bessel filter, or an 8th-order Chebychev filter, only the Chebychev filter option will be available to choose from.
Figure 4: Filter Design Aid Summary