Am 10.07.19 um 11:27 schrieb Bruce Griffiths:
Like virtually all low dropout regulator ICs the LT3042 is quite noisy at
frequencies below its reference low pass filter high frequency cutoff. Some
zener based references are considerably quieter in this region.
We had that already last year.
I have delivered measured curves that show that it's not true.
The trick of the LT3042 is that it's reference is not very noisy,
and there is NO VOLTAGE GAIN after the reference. Zener-based
reference diodes are _much_ worse, and the LT3042 can hold
the candle even to 2V7-Zeners and most LEDs.
You can filter the LT3042 reference quite heavily, and there is
a startup circuit so you do not have to wait too long for the output voltage
to become stable.
common Regulators:
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https://www.flickr.com/photos/137684711@N07/24070698809/in/album-72157662535945536/
>
Zeners: (Look at that awful super-precision ovenized LM399!)
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https://www.flickr.com/photos/137684711@N07/24411798996/in/album-72157662535945536/
>
LEDs:
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https://www.flickr.com/photos/137684711@N07/24354944411/in/album-72157662535945536/
>
King of the LEDs is hp/Avago/Broadcom HLMP6600, if it is still alive.
I plan to repeat these measurements in the close future with a new
FET-based amplifier that
is not challenged by that stronger-than-1/f low frequency noise and that
can use cross correlation
additionally because of its missing noise current.
regards, Gerhard.
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