K
It is generating 0.1V across the 1mΩ (shunt) resistor so I think it is correct.I_dc 300A ? Confirm that.
Regards, Dana.
A simple, conventional differential amp with a single opamp and four resistors is all you need.
See the "Operational amplifier as differential amplifier" section in this article:
Differential amplifier - Wikipedia
en.wikipedia.org
The two input resistors should be equal.
The two feedback & reference resistors should be equal. The ratio of those to the input resistors defines the gain.
The point the ref resistor (Rg) connects to defines the output voltage when the inputs have zero difference.
Well, that is confusing.I am afraid that this simple conventional differential amp works only if its two inputs are independent of each other.
This is nonsense. A differential amplifier imposes no such restriction on the inputs. Any particular amplifier that you can buy may have range restrictions on the inputs, but nothing requires them to be or not to be related. The transfer function just does what it is designed to do.Thank you for replying.
I am afraid that this simple conventional differential amp works only if its two inputs are independent of each other.
Here if V2 decreases, V1 decreases too. That is V1 is a function of V2.
But I also understand that as long you don't have time to simulate what you proposed (as I did already before I started this thread), you have to believe that the conventional differential amp also works here.
I am afraid that this simple conventional differential amp works only if its two inputs are independent of each other.
Here if V2 decreases, V1 decreases too. That is V1 is a function of V2.
That's putting a pretty fine point on the matter.The only restriction on that style of differential amp is that the opamp +input voltage must always be within the common mode range of the device chosen.
That voltage is produced by the +input and reference resistor divider, the ratio of which depends on the gain K.
(And, obviously, the output voltage after gain must be within the opamp o/p voltage range on the supply in use).
Any general opamp which includes V- in its common mode range, and is rated for 30V single supply should work fine.
As long as the resistor values are chosen correctly, the output voltage relative to the ref point will be equal to (V1 - V2) * gain.
What does "the node AUX could be connected at will" mean?I am very sorry. It seems I wrongly simplified the schematic of the problem above. So just to complete the topic, I attached the updated one below. Now, it looks like the case of a hi-side differential amplifier (though R2 is not a sensor here). Although special ICs are made for hi-side sensors, they may not be suitable for a relatively high voltage on it (here, it is V1-V2 on R2 where V2 is close to ground). Also, I avoid, as possible, using special ICs while I have a lot of conventional opamps.
Anyway, it is up to you now to try sharing your ideas or not about a practical solution. On my side, I am sure I will find one which could be rather simple and suitable for the project I am working on.
Best wishes,
Kerim
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