[sdiy] Moog ladder matching

[Magnus Danielson]

From: harrybissell <harrybissell at prodigy.net>
Subject: Re: [sdiy] Moog ladder matching
Date: Sun, 13 Mar 2005 17:18:22 -0800
Message-ID: <4234E659.6220E833 at prodigy.net>

> IMHO the thermal coupling might not be that much of an issue... as the
> self heating should be small (maybe 1mA max current)... and it will be matched.
> 
> IF they are not in a isothermal environment. Put one next to a power resistor
> and
> all bets are off...

Which is what I am mostly worried about, temperature gradients. Put a metal
wrapping around each pair and they "see" more or less the same temperature
radiated in or rather in lack of cooling radiation out.

Putting the whole board of transistors in a metal case should also work well,
since metal conducts better than radiation through air, so any external
temperature gradients is greatly dampend to become a more common surrounding
temperature. It is not in itself a temperature stabilisation, it is just to
ensure the different chips see more or less the same temperature all the time.

Glueing the transistors together connects them thermically better.

But then, having static bias-flaws doesn't help either.

Why does transistor-arrays sound so sane and cheap all of a sudden?

Cheers,
Magnus