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Reading a voltage when there are ground drops?

Flyback

Well-Known Member
Hi,
Do you know of a lower component count solution for the following?...
As you can see, there is a Diff Amp which reads a 3V source voltage…..then passes it to circuitry which is grounded to a slightly different potential….and that circuitry there must read the 3V voltage correctly.
The attached does it but is too high in component count. Do you know of a lower component count way?
 

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  • Diff Amp for when there are ground drops.asc
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  • Diff Amp for when there are ground drops.jpg
    Diff Amp for when there are ground drops.jpg
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rjenkinsgb

Well-Known Member
Most Helpful Member
I am not sure why it has to be so?..........After all, as long as you can put the currnt sense max voltage on the share bus, and then get it back off again, then i dont see why it has to have the single point ground connection?
Because it is a differential bus!

Share- has no drivers at all. Without an external reference for that, the whole thing is floating and nothing can work properly, there is no reference point to have a "difference" from; nothing to hold it within a sensible common-mode range.
 

Flyback

Well-Known Member
Share- has no drivers at all. Without an external reference for that, the whole thing is floating and nothing can work properly, there is no reference point to have a "difference" from; nothing to hold it within a sensible common-mode range.
Thanks very much, i think this is just exposing my lack of electronics knowledge and my lack of ability to explain what i mean....the simulation in post #15 works well, and the SHARE- node isnt directly grounded anywhere. So i am not sure what it is, but it works well, and i'd like to keep with it....just that the component count is very high.
I dont believe it to be "floating" as there is no isolation in the circuit of #15.

So it appears to me that even though i have been asking for a "differential bus".......i most probably mean something else...what i mean is the "situation" of #15.......the share bus takes on the voltage of the highest output current sense amplifier, and at each lin. reg. stage, that voltage is correctly "recieved", so to speak.

The result is very good sharing between the lin. reg.s.....even though they have different ground potentials to each other....and their upper output voltage divider resistors are slightly different.
 

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