DIY parts

[terry michaels]

-------------Forwarded Message-----------------

From:   terry michaels, 
To:     INTERNET:jhaible at metronet.de, INTERNET:jhaible at metronet.de
        
Date:   8/23/98  8:57 PM

RE:     Re: DIY parts

Message text written by INTERNET:jhaible at metronet.de
> But still, a few points to add:
> (1)You could use a guard ring without a virtual gnd node, too.
> Connect it to the buffer output instead.
>(2) You can use an extra transistor for a cascode configuration
> if you want to keep the cb voltage of the expo converter's transistor
> low. This will also help making a high output impedance.
> Korg used an extra FET for this cascode configuration in some of
> their VCOs. (Expo converter from dual npn, output drives FET with
> base grounded, discharge circuit is a thyristor built from discrete 
> npn's and pnp's, and buffer is another FET. 
> I do *not* know how good this performs, but I thought I should mention
it.

Hi Jeurgen:

You're absolutely right, of course.  Havn't seen the Korg stuff, but I'm
not surprised about the cascode idea. That is a clever approach. 

There has been a lot of VCO designs in the last 30+ years, I think almost
everything has been tried by now.

Terry