2nd generation VCFs (was: Xpander VCF)

[Magnus Danielson]

From: jhaible at t-online.de (jh.)
Subject: Re: 2nd generation VCFs (was: Xpander VCF)
Date: Thu, 26 Oct 2000 01:34:47 +0200

> > Right. I would strongly advice you to read the patent behind the SSM
> > 2044. It is US Pat. 4,404,529. That patent expired in 1995 BTW, so
> > it's content is out for grabs!
> 
> I guess I have to confess something: I have the patent paper for years,
> but I never read it. Just looking at the pictures. I thought everything
> was clear, and I never bothered about reasons for a different final
> stage. So there is a description about that HF bleedthru in there ?
> Funny !

The bleedthru may not be covered, but there are many other aspects...

> > Juergen or someone else should find it easy to conver a lump of BC550
> > and BC560 (or 2N3904 and 2N3906 for our american listeners) into a
> > full-fledged filter.
> 
> I thought most of that "folding" the cascade into current mirrors was just
> about fnding a way around the Moog patent. (?) Easy to have such a huge
> number of matched transistors on a chip, but a pain to match so many
> discrete devices.

I'd rather say it's a diffrent approach in it's own right. The
alternatic comes from the goal of avoiding additional current mirrors.

> > Go and read the patent.
> 
> I will ! (;->)

Goodie.

Cheers,
Magnus