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Author Topic: [question] : virtual ground ?  (Read 836 times)
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omidsht
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« on: February 28, 2008, 08:37:38 08:37 »

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
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Posted on: February 27, 2008, 06:48:06 18:48 - Automerged

no body can help me ?
 Huh Cry
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bajrang
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« Reply #1 on: February 28, 2008, 09:52:10 09:52 »

Dear friend,
please look at the schematic attached.
Hope it solves your problem.
regards,
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FriskyFerret
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Put it in, take it out.


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« Reply #2 on: February 29, 2008, 03:23:41 15:23 »

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

Is that plus and minus 6 volts AC or DC?
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omidsht
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« Reply #3 on: March 02, 2008, 05:28:35 05:28 »

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
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caveman508
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« Reply #4 on: March 02, 2008, 06:11:09 06:11 »

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

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