Building an analog Low Pass Filter using PSoC3 Analog

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    Question: Can I build an analog filters using PSoC 3/5?              (or) Can I port a PSoC1 filter to PSoC3/5?



    It is not possible to build a totally internal analog filter( LPF/BPF/HPF/BSF) in PSoC3/5. That means you cannot port an existing PSoC1 filter to PSoC3. This is because the SC block structure in PSoC3 is different form that of PSoC1 and does not support filter construction. (see differences here). However, the uncommitted opamps on the chip can be used to build filter using external passives.

    Standard filter topologies built around Op-Amps like the Sallen Key, Multiple Feedback, Bi Quad, State Variable should be built around naked Op-Amps with external resistors and capacitors.


    Sallen Key

    Multiple Feedback

    Bi Quad

    State Variable


    1. In the above images of various Topologies, only OpAmps of PSoC3/5 can be used. All other resistors, capacitors and inverters are to be used externally.

    2. The Filter component available in PSoC Creator Components catalog is a Digital Filter - FIR.