Electronics > Metrology

ADR1001 - Ovenized Voltage Reference System

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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.



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 :-//

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.

@Noopy: shouldn't be there p+ beneath the Anode Sense in your picture above (ADR1001)?

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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