# conversion of 0-5v input to 0-3v output using op amps

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#### ppstar375

##### Newbie level 2

You can use a simple resistive voltage divider. You may add an analog buffer (employing a simple opamp voltage follower circuit) at the output of the voltage divider.

Hope this helps.
Tahmid.

Thanks Tahmid for replaying..yes i too found the voltage follower circuit good enough, the only difficulty i am finding is that the op amp needs to be supplied with 3.3v as common mode voltage (Vcc), i am not finding if any such op amp is present in market. i mean if i wud know the ic number it will be easier for me to order it.it would be nice of u to help me out in this. thanks for ur consideration anyways..
(ps: there are many op amp available such as LM3940, but they give a fixed output of 3.3v for voltage input of 4.5 to 5v,,whereas we require is for 0 to 5v input we should get 0 to 3.3v output.)

there are many op amp available such as LM3940, but they give a fixed output of 3.3v for voltage input of 4.5 to 5v

But the 5v in not supposed to reach the opamp input, first there is a divider /0.6 and then the resulting voltage feeds the opamp buffer

Tahmid didnt mean use a resistor divider with an op amp, as he said, resister dividers would be usable if all you are doing is scaling your output. Vout=Vin*(R2/R1+R2). so set 3.3/5 = R2/(R1+R2)=.66 so a R2=10k and R1=5.15k would do the trick.
if you want it buffered then you should use the op amp, and then you could merge the resistor divider into the buffer to get a circuit like you posted above. if you dont need an op amp, dont use 1. I find it apparent op amp theory is beyond you and so recommend not using one.
-Pb

simply use this voltage divider so 0 will give 0 and 5V will give 3V.

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