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From: markf@amc-gw.UUCP (Mark Freeman)
Newsgroups: sci.electronics
Subject: Re: State Variable Filters
Summary: Why this is called a State Variable Filter
Message-ID: <820@amc-gw.UUCP>
Date: 8 Sep 89 17:50:06 GMT
References: <2376@radio.oakhill.UUCP> <17660018@hpfcdj.HP.COM>
Organization: Applied Microsystems Corp.; Redmond, WA
Lines: 18

In article <17660018@hpfcdj.HP.COM>, myers@hpfcdj.HP.COM (Bob Myers) writes:
> >works but WHY is it called a 'state variable' / 'biquad' filter???
>  
> a biquadratic transfer function, but I'm not certain how "state variable"
> got hung on this particular circuit.  (There is at least one other three-amp

I believe the term "State Variable" is applied to this circuit, because the
terms of the State Coefficient Matrix apply directly to the amplifier
transfer functions.  Thus, you can go back and forth between the matrix
representation and the circuit readily.  Take this explanation with a grain of
salt, as it comes from someone who has worked on software and digital hardware
for the last 10 years.

-- 
				Mark S. Freeman
				Applied Microsystems Corp.
				markf@amc.com
				amc-gw!markf