[sdiy] Passive filters and impedances

[Donald Tillman]

Instead of turning to a symbolic math program, I think it's a lot more educational, self-reliant, and true to the DIY spirit to just do it yourself.  It's not difficult, and it's an important and useful skill to have.

Here, I'll help get you started.  For the two pole circuit, let Va be the voltage at the junction of R1, R2, and C1.  The sum of the currents going into this junction must be zero.

(1/R1)(Vin - Va) - (1/sC1) Va + (1/R2)(Vo - Va) = 0

Rearrange that into the junction order, by the V's:

(1/R1)Vin + (-1/R1 - 1/R2 - 1/sC1)Va + (1/R2)Vo = 0

Next, do the same for junction Vo, and you're well on your way.

  -- Don

--
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com