[sdiy] Filter Structure Question

[Magnus Danielson]

From: Scott Gravenhorst <music.maker at gte.net>
Subject: Re: [sdiy] Filter Structure Question
Date: Fri, 16 Jul 2004 13:15:50 -0700
Message-ID: <200407162015.i6GKFoZ11026 at linux6.lan>

Scott,

> Pictures being worth many more than a thousands words, here is what I have envisioned:
> 
> http://home1.gte.net/res0658s/CMOS_SVFb.gif
> 
> The 4007 power pins are both open.  All of the inverters come from the same 4069UB
> package.  The ground symbol is the signal and CV ground, whereas the 0volts and
> 5volts terminals are just the regulator outputs.  0volts is not connected to
> ground.  Resistor values are SWAGs (SWAG = scientific wild ass guess).  From what I
> read below, you would suggest 100 ohm as a SWAG for each power supply feed resistor.
> 
> Am I close?  Or are you talking about a more specialized power supply system?

Yes, you are bloody darn close!

First of all, I where considering +5V/-5V supply. When driving the ground like
that you need the negative side, and also, the signal will go there. 

Then, beware that the MOSFETs only act properly for one current-direction, so
you need the compelements, so you should be using the spare inverter to invert
hthe CV signal accordingly. 

Then, you have marked the HP output as output, so this is a HP filter as it is
drawn, but it should be simple enought for you to draw the other outputs 
aswell.

Also beware that the drive-levels for the MOSFET VCRs can't bet that great.
Not the usual +/- 5V or more as normally seen. 

You might consider some diode-limiters in the feedback path. Then again, you
might not. ;O)

Cheers,
Magnus