[sdiy] Negative voltage references

[Tom Wiltshire]

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