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Analog Filters: a Compilation of Standard Transfer Functions (UPDATED)

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--- Quote from: Dunckx on March 28, 2021, 10:28:14 pm ---I have just discovered that Zverev's "Filter Synthesis" book is out of copyright and may be downloaded from the Internet Archive for free!


--- End quote ---

Great handbook I didn't know before, thank you!   :)

It even shows the "N-Path mixer"/"PolyPhase Mixer" at page 35/586, "Fig.1.33 The Digital Filter", recently discussed in

--- Quote from: Zverev's "Filter Synthesis" ---A   method   having   the   dimensions   of   a   genuine   breakthrough  is  shown  in  Fig.  1.33.   Here  the  mech-anical  commutators,  shown  schematically,  would   be   replaced  in  practice  by  transistor  diode  analog-gates  driven   by  conventional   logic  circuits  at  an   angular   velocity,  co0.  The  identical  RC  circuits  have  a  lowpass  response  which  is  so  modified  by  the  sampling  action  that    VJV2    exhibits    a   related    bandpass    response    centered    at    a>0.    This   method    shows   promise    of    yielding  figures  for   Q  and  stability  which  have  pre-viously    been   obtainable    only   with   crystal   filters.   Definite  results  on  the  performance  of  this  device  will  be    available  soon,  but  it  is too  new  to  be  evaluated  at  present.

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Yes, even Zverev referred to this commutating filter, which even predates Zverev's classic reference book by a few years!! However, these Discrete Time Continuous Amplitude (DTCA) filter concepts for other uses evaded general discovery until the Tayloe's Detector in the late 90s and then the PolyPhase, or N-Path Mixers ~2008. We did employ the DTCA commutating filter (as well as DTCA Chirp-Z techniques for Real Time SA) techniques in the early 80s for a narrow band tunable RF filter, but it took another 20~30 years for "other" uses of this very powerful technique to emerge!


For just getting to work on a filter without all the synthesis, Analog Devices has an awesome tool:


Define low/high/bandpass and passband/stopband needs, and boom you get a schematic.  Not only can you view mag/phase... you can specify cap and resistor tolerances and see the sensitivity envelope.  The recommended opamps are ADI, of course, but you can look up the gain-bandwidth and such to determine substitutions for each stage.  Plug it all into ltspice and fine tune.  ADI make great components, though I am more partial to ti opamps as they are usually cheaper than adi for the same performance, and cmos opamps (eg: opa2376) are finally getting into the realm of really low noise for low-power/low-volt applications.


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