Filters Tutorial Episode 9: The Sallen-Key Second Order Active Filters

Presenting the Sallen-Key filter topology, an easy to design and analyze active filter that can be adapted to work as any kind of filter, from Low Pass, to High Pass and Band Pass.
This video goes through the theory behind this type of filter and shows a design example of a 2nd order low pass filter.
To better understand the contents of this video it is recommended to first view the previous episodes of the series, especially episode 5, first order high pass filters, which introduces the concepts of transfer functions, poles and zeros:
• Filters Tutorial 5: Pa...
Happy Experiments!
Link to the tutorials series:
• Filters Tutorial Episo...
On-line circuit simulator, from PartQuest (Siemens):
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Thank you for watching!

[@Bnels]

This is one of the best tutorials I have watched. Thank you so much!

[@raefsiam]

good work , thank you

[@mirunavlasceanu706]

Thank you so much, it helped me so much!

[@eleneasy]

I'm so glad!

[@mirunavlasceanu706]

@@eleneasy I also got a question, It's okay to cascade two second-order circuits (with the same capacitor and resistor values) to achieve a fourth-order filter? or it will impact da quality factor?

[@eleneasy]

@@mirunavlasceanu706 Yes, as long as they are active filters, you can cascade two second order filters to make a fourth order filter. However, the quality factor, or Q, also changes. In particular, if you use two identical second order filters, the new Q factor becomes sqrt(2) times (about 1.41) the original Q factor of each filter. If the two filters are different, then it is necessary to study the transfer function of the newly formed 4th order filter to understand how the Q changes.