vivkr
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Hi Frank,
You can generate such a floating voltage in several ways. One way is to use a DDA (Differential Difference Amplifier). This has 2 sets of differential inputs. For some information on this, you can refer to the JSSC paper by Sackinger and Guggenbuhl.
"A Versatile Building Block: The CMOS Differential Difference Amplifier", JSSC, April 1987.
You must keep in mind though that DDAs suffer from various performance limitations and might not be practical for your task.
Another option is using a fully differential difference amplifier. Such a block is widely used in analog design. You will need 8 resistors and a fully differential opamp though, not to mention a CMFB for this opamp.
If you are planning to use this floating voltage reference as a CMFB for another opamp, then you will quickly discover that stabilizing the circuit is nontrivial.
Iif you want to track 2 mutually varying voltages to generate a floating supply, you may have to do something like this. However, if the 2 voltages are question but only with a fixed difference, a level shifter may be all you need.
Hope this helps.
Regards Vivek
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