| Electronics > Beginners |
| Analog bandpass filter - bode plot for various filter types |
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| petert:
Hi, I have tried various calculators, and also calculated by hand, but when I simulate the circuit in LTSpice I do not get the expected results (passband bandwidth is not narrow enough, center frequency is off, or output voltage too low, etc.). So I'd like to take a more systematic approach. Is there a program that can draw bode plots for all common analog filter types, for a given/set center frequency and passpand? What I found is usually limited to special circuits, or 4-stage opamp only circuits, but I haven't found an all in one solution, that allows easier comparison. Great would be if it would consider crystal based filters, LCR based filters (or LC, LR), and those using opamps, and show their performance in comparison. |
| voltsandjolts:
Microchip FilterLab - but IIRC only does Bessel/Butterworth/Chebychev |
| ogden:
--- Quote from: petert on September 22, 2018, 06:39:36 pm ---Is there a program that can draw bode plots for all common analog filter types, for a given/set center frequency and passpand? What I found is usually limited to special circuits, or 4-stage opamp only circuits, but I haven't found an all in one solution, that allows easier comparison. --- End quote --- For opamp based RC filters you shall try Analog Devices filter wizard. It has bode plot as well. Professionals use commercial tools like Genesys to design and simulate circuits including passive filters. For amateur/hobby use there are many online filter calculators. Your results may differ due to different Q factor of components in design versus simulation and maybe impedance mismatch. Filter shall be fed and loaded using impedances it was designed for. I know that http://www.wa4dsy.net/filter/filterdesign.html does work correctly and LT spice simulations match. Thou I was using lowpass filter calc. |
| T3sl4co1l:
Don't forget that filter tables don't account for inductor or capacitor Q (except those that do, but only to the extent that they can), and LTSpice has default values for components that you need to specify if you're doing other than those defaults. Tim |
| petert:
Thanks for the links. I tried it, unfortunately with no luck. Probably doing some beginner mistakes. Edit: looks, better now. See post below. |
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