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Assistance needed to convert single ended signal into differential signal

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bodenste

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Hi,

I have the following situation and am uncertain how to proceed:

* Input voltage 0V to 5V (single ended signal)
* Output voltage: differential output, 2V p-p

I have a fully differential op amp that I believe is set up correctly (Rf = 400, Rg = 1k, Vocm = 2.5V, +5V rail and ground rail).

If I input +2.5V to -2.5V I get exactly the correct output :
* Vin@ 2.5V -> Vout+ = 3V Vout- = 2V
* Vin@ 0V -> Vout+ = 2.5V Vout- = 2.5V
* Vin@ -2.5V -> Vout+ = 2V Vout- = 3V

However, I do not have Vin = 2.5V...-2.5V. I have Vin = 0...5V.

What is the best way to adjust my input voltage? Do I need an additional op amp? I do not currently have a negative voltage rail but I suppose I could create one using a charge pump IC.

Is there some other clever way to accomplish this?

Thanks!
 

FvM

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You simply can connect the negative input to a 2.5V reference voltage
 

bodenste

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Ha! I knew there was a trick. That works perfectly, thank you so much. Does it matter how much current goes in? And, if the Vocm outputs 2.5V based on a 5V rail input, any reason I shouldn't use it?
 

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