set 4461 common mode dc offset

[nickstorton]

Hi all,

Does anyone know if it is possible to programmatically set a common mode DC offset to the differential output of a 4461 or do I need to do this with external components? Please note that this is a different requirement to setting the differential DC level which I know you can do.

Thanks,

Nick

[Larry_Morgan · Accepted solution]

Hi Nick,

Thanks for the question. We currently do not allow the user to directly set the common-mode offset of the output. In differential output mode, both the positive (BNC center) and negative

(BNC Shell) outputs have 2.4 KOhms to earth ground (it is not isolated from earth ground). Because of this, in essentially all cases, whatever components you introduce to move the common-mode

offset of the output will also introduce a differential gain error as well. Also, because of the lack of isolation, there is a limit to how much the common-mode offset can be driven away from earth ground.

This would also depend on the magnitude of your output signal. As you approach the limit, there will be a noticeable increase in distortion which will turn to full clipping eventually. 

I hope this helps answer your question. 

-Larry