I want to design passband filter.center fre=14000 hz band w =4000 stop atn =-35 i have some questions
1-)i have designed but resistor value are odd like 28,63 k ohm...% 0 tolerance.... is not this a problem how can i get this value...
2-)sallen key or M feed back which we prefer_?
3-)which opamp we prefer_?
thanks
Koray,
When FilterPro first does a design, it uses exact resistor values (0%) - you can then change this by using the controls at the top right of the schematic screen:
You can set both resistor and capacitor tolerances, and FilterPro will find the nearest standard value to match your design requirements.
The choice of Sallen-Key or Multiple Feedback topologies depends upon your requirements. Each second-order Sallen-Key stage is a non-inverting design, while each MFB stage inverts the signal. Depending upon your circuit and application, you may or may not want the signal inverted. There are instances where the Sallen-Key topology is a better choice. At unity-gain, the Sallen-Key topology inherently has excellent gain accuracy. This is because the op amp is used as a unity-gain buffer. With the MFB topology, gain is determined by the R2/R1 resistor ratio. The unity-gain Sallen-Key topology also requires fewer components—two resistors versus three for the MFB.
The best filter design may be a combination of MFB and Sallen-Key sections. To do this, use FilterPro to define the component values of the same design using both circuit types, and then use some of the sections from one design with some from the other design to build your filter design.
When your design is complete, you'll find some information about each stage displayed below the schematic. The minimum gain-bandwidth (GBW) for each op amp used for each stage is shown. This is the critical parameter for choosing the op amp(s) to use in your filter.
I hope this answers your questions. Thanks for your interest in FilterPro.
