[time-nuts] Linear voltage regulator hints...

Didier Juges shalimr9 at gmail.com
Tue Dec 9 21:44:58 EST 2014

That seems to be generally true, but as always there are outliers.

The LT1034 bandgap reference has 6uVp-p of low frequency noise at 2.5V,
which compares favorably with the 20uVp-p of noise at 6.95V of the LM399.
Of course, for many applications, you will have to amplify the 2V reference
to what you need, which will bring up additional noise while the 6.95V of
the LM399 may be closer to what you need.

Of course, the tempco of the LT1034 does not even get close to that of the
LM399, but it is not thermostatically regulated and draws considerably
lower power. You can't have everything :)

I observe that the LT1034 has two outputs, the high quality 2.5V and a
lower quality 7V.


Didier KO4BB

On Tue, Dec 9, 2014 at 5:51 PM, Richard (Rick) Karlquist <
richard at karlquist.com> wrote:

> On 12/9/2014 1:30 PM, ed breya wrote:
>  buried zener for lowest noise - this eliminates all the low voltage
>> references and three-terminal etc regulators that use band-gap
>> references. The down side is that the good kind of reference ICs will
>> need a higher (like 10V and up) operating voltage than may be available,
>> so that complicates it.
> Great post, Ed.  I might add that my understanding of band gap
> regulators is that they rely on amplifying a small DC difference
> in voltage between two transistors.  This also amplifies the SUM
> of the noise of the respective inputs, which jacks up the noise to
> much more than a good zener.  Because of physics, no band gap
> reference will ever be low noise.
> Rick Karlquist N6RK
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