ada4950-1 vocm problem?

Noise gain?

Supplies?

resistor values?

schematic?
Harry

Dear Harry,

the circuit i have used is attached

azita 

Hi Azita,

Thank you for sharing your schematic. May I know what's the signal frequency? Cause aside from input offset voltage, one thing that might add into the imbalance is the noise from the gain setting resistors. Also, is your input from a clean source? Means no dc offset at all. In single-ended configuration, a 10 mV input offset would cause an imbalance at the Vocm. Just to check.  

Regards.

Dear Jinol,

the frequency of our signal is 300MHz and it has no dc offset voltage . i checked the supply voltage with battery without any noise and see the output voltage is same as past. in addition i grounded the inputs and check the output and saw the same result and the problem did not solve!about the gain setting resistor is there any way that we do not see this noise at the output?

Hi Azita,

Actually, the Vocm is specified + 6 mV input offset voltage. By that, you are within the operating specs of the part.

And btw, apologies for not replying on your previous query. We can't do anything in reducing the noise contributions on the gain setting resistors since those are internally connected. Please see Tables 12 and 13 of the datasheet for the details on the noise at different gain configs.

Regards,

Jino

Hi, i replaced the resistors and could improve the offset to 3mv , i checked the circuit in the multisim and saw there is always  an offset of 3mv . is that really correct for this part?

Dear Jinol ,

thanks for the that , it really helped me .you are right and my circuit is in its normal working.best regards