[sdiy] Re: Maths for filters

[Neil Johnson]

Florian,

> Do you have any resources for calculations of filter circuits (state
> variable)?

The keyword here is "Laplace", ie. s-plane maths.  My current filter book
I'm using (although I have quite a few others) is:

	"Principles of Active Network Synthesis and Design"
	Gobind Daryanani, (Wiley, 1976)

which is full of maths on Biquad sections, state-variable filters and the
like.  Essentially, treat s = jw and convert everything to the s-plane.
So, for example, one of my integrators would "-F/s" (where F is the
gain of the gain cell, corresponding to the Frequency CV, and the 1/s term
represents the integrator function).  Then sketch out the circuit using
s-terms and convert into equations.  Then solve.  Easy :-)

> I only have some books I use for my electronics studies but nothing is
> mentioned there.

Ahh, well, in my day (!) there were lots of control theory (which helps
understand the whys and how of filters, damping/resonance, etc) and
analogue filter design.  I did one telecomms course that was ALL Laplace
transforms and the like.  Comes in real handy for designing filters and
oscillators.

Just do a search on google for "laplace transform"...  (34,000 hits)

Hope that has pointed you in the right direction.

Cheers,
Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
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