Electronics > Metrology
ADR1001 - Ovenized Voltage Reference System
Noopy:
I have updated the pictures/text on my website with the hint magic gave us. :-+
This is the ADR1000 structure.
I now assume in the ADR1001 it looks like this. The emitter is missing and the contact in the middle changed to a Anode Sense.
If you look closely and compare it with the ADR1000 structure you can see that there is a ring missing. That is the emitter area.
The big pictures looks like this.
https://www.richis-lab.de/REF29.htm#Update
:-/O
magic:
You could add the connection between anode force and the isolation island to your cross section diagram.
(And link the other ADR1000 image with section lines marked on it).
Now I don't understand why they removed the transistor from there.
Substrate connection had to go for obvious reasons, but it looks like the transistor could remain inside and still work normally :-//
Noopy:
Are you sure there is a connection between Anode Force and Substrate?
We don't see a segmented collector feed. My assumption is that the whole circuit is embedded in a closed collector well.
That would isolate the zener and on the other hand there is just a minor increase in resistance. But the resistance is not critical since we have a sense pin.
With this in mind it makes sense that they had to delete the transistor.
They had to get a Anode Sense contact and perhaps the increased base resistance (without the use of the substrate) would have been problematic.
iMo:
@Noopy: shouldn't be there p+ beneath the Anode Sense in your picture above (ADR1001)?
Noopy:
I don't see an additional structure and I don't think it is necessary.
"Normal p" has a little higher resistance but it is just the sense connection with low currents. In a transistor "normal p" is good enough for base connection too.
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