[sdiy] improved dynamic range diffpair-vca

[HOSHUYAMA]

Aaron,

What a coincidence!

The dolby's patent shows a variable resistance cell using a differential 
pair with a lot of diodes at the common emitter (Fig. 6).

  http://www.pat2pdf.org/patents/pat4068139.pdf

  An OTA with 100% feedback works as a variable resistor.

It was published in 70's.  So, the Japanese patent application 
can not be patented  ;-)

Sam Hoshuyama
Saitama, JAPAN


From: Aaron Lanterman <lanterma at ece.gatech.edu>
Date: 2007/04/26 03:28:30
> 
> On Thu, 26 Apr 2007, HOSHUYAMA wrote:
> 
> > Actually, what I saw the circuit topology was a patent application (In 
> > Japan, almost all the patent applications becomes public after one and a 
> > half years.) not a filed patent.
> >
> > A couple of years ago, I saw the same structure in a Japanese 
> > electronics book published in 80's. I guess, the structure was not 
> > patented.
> 
> Interesting! Thanks!
> 
> - Aaron
> 
> -----------------------------------------------------------------------------
> 
> Dr. Aaron Lanterman, Asst. Prof.
> and Demetrius T. Paris Junior Prof.  Voice:  404-385-2548
> College of Electri. and Comp. Eng.   Fax:    404-894-8363
> Georgia Institute of Technology      E-mail: lanterma at ece.gatech.edu
> Mail Code 0250                       Web:    users.ece.gatech.edu/~lanterma
> Atlanta, GA 30332                    Office: Centergy 5212
> 
>