[sdiy] Negative voltage references

[Harry Bissell]

I like shunt references like the LM336 (-2.5, -5 etc)  They are used like
zener diodes so they are applicable for positive or negative references.

The LM4040 is good as well.

If absolute voltage is not a requirement (only stability) a 5.1 zener diode
makes a near-zero tempco reference (5.1 is the "magic" voltage for zener temperature coefficient)

H^) harry

----- Original Message -----
From: Tom Wiltshire <tom at electricdruid.net>
To: Neil Johnson <neil.johnson97 at ntlworld.com>, David G Dixon <dixon at mail.ubc.ca>
Cc: synth-diy at dropmix.xs4all.nl
Sent: Sun, 20 May 2012 10:43:55 -0400 (EDT)
Subject: Re: [sdiy] Negative voltage references


On 20 May 2012, at 14:45, Neil Johnson wrote:

> Hi Tom,
> 
>> As I said, I'd have used a 79L05 if I'd had one. The chunky 7905
>> isn't doing the job without enough current pulled out of it.
> 
> Well, even the 79L05 has a minimum current requirement.  According to the TI/NS datasheet it's only 1mA, but it's still a requirement to be in spec.

Well, at least that's an improvement on the 5mA or so minimum that the 7905 needs!

1mA pulled from my -5V voltage is a total resistance less than 5K. It's true that currently I'm still well above that, since most of the CV op-amps have 200K input resistors for the offset, and you need a lot of those in series to get 5K. Still, I can always bang a 4K7 or 3K3 across the regulator output.

How do you deal with the minimum current requirement in your 2164 VCAs, David?

Thanks,
Tom

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-- 
Harry Bissell & Nora Abdullah 4eva