[SOLVED] How to selection common mode voltage

[jiangwp]

When ic is working for a range power supply , i want to know how to design for the the common mode voltage of full diffential operation amplifier but not to degrade more performance.

 

[huanchou]

I think this is decided by the input range of the next input stage that will be the op's output.
In my view, 1/2(Vrange,next input) is better.

 

[sunking]

It depond on you system.
In fact, some is the same of input voltage, some is 1/2Vdd, some is a fixed voltage

 

[jiangwp]

I mean the ic work in multiple supply power.
If the common mode voltage is fixed voltage, it wil not fit for the power supply variation.
But if the common mode voltage is variable (like the vdd/2), i want to know how to generator. I think the
resistor divider is not fit for it , as the power supply is interfered by the noist spike of digital part.
On the other hand , the vdd/2 may be not the best selection for the SNR and DR. I want to know whether there are other ways for suring the performance with the varing power supply.

 

[aryajur]

You could try using a series connection of diode connected transistors from Vdd to Vss and then tap any point between any 2 transistors to get a particulat fraction of your supply and it will change as supply changes