[question] : virtual ground ?

[omidsht]

Hi ,
i have two differential signals , when one is +6 the other is -6 , and vice versa , and when one is null the other is null too . i want to build a virtual ground for them to compare them to that virtual ground , (actually i want to rectify them and take them to microcontroller , so i nee d a ground and i dont want to take a gnd line from the source) , can any body suggest a circuit to buld a virtual ground for them ?

thanks
omid
 

Posted on: February 27, 2008, 06:48:06 18:48 - Automerged
no body can help me ?
 

[bajrang]

Dear friend,
please look at the schematic attached.
Hope it solves your problem.
regards,

[FriskyFerret]

(actually i want to rectify them and take them to microcontroller)

Is that plus and minus 6 volts AC or DC?

[omidsht]

that shematic does not work , it has a lot of noise on output , we have + and - 6 volt as a pulse wave (dc) with frequncy of 100khz .
the above shematic did work in simulation but not in real .
so to have a test , i just used two 33k resistors in series , one end 6 volt fiexed , the other end -6 volt fixed , then i put the gnd of oscope in the middle of those two resistors (which should be zero accordinf to kvl) and the probe of oscope on the +6 volt end , it was really noisy .
why ?
i dont know !
and this is why the above circuit does not work for me .
any oppinion ?
thanks
omid

[caveman508]

I am not an analog engineer, but I see no capacitors in the design..  Maybe some on the supply, and a bit on the voltage divider???

Just a guess, they do amazing things.

Caveman