The output of Op-Amp[LM324] has error as non-inverting Amp

[booboo1]

Hi everybody
I'm a newbie and working on LM324 to learn Op-Amp. this is my circuit:

http://img4.uplood.fr/free/qx3o_20150425_172843.jpg
One of the resistors is 217ohm and another 978ohm. then the gain should be 4.50691 as you can see. so far so good. I know this is for ideal Op-Amp. I applied 0.15v to the input and got 0.94v in the output. then the gain is 6.26667. again I applied 0.35v to the input and got 2.03v then gain should be 5.8!?
again I applied 1.86v and got 10.31 then the gain is 5.54301! holy crap! why isn't the gain stable? because of input offset voltage? How can I stabilize it?

 

[Averagesupernova]

You need a split supply to make this work.

 

[jim hardy]

LM324 should be okay with single supply so long as everything stays positive,.
But if you're inputting AC then yes, you need dual supply.

Did you bypass your supply with a small cap near the IC?

What is voltage at junction of 217 - 978 resistors?
Is it the same as your input?
If opamp is making its inputs equal , the problem is not offset.

Possibly it's your layout. When power supply current shares a wire with signal, the drop along the wire adds to signal.
Is there any AC in your output?
How are your input source and 217 tied to common ?

 

[Averagesupernova]

The gain for a non-inverting op-amp is not how you are computing it. The gain in this case is 5.50691. (978/217) + 1. Keep your input voltages farther away from the supply rail with a 324.

 

[jim hardy]

The gain for a non-inverting op-amp is not how you are computing it.

Thanks - i missed that !
Big ten-duh on me, good buddy !

 

[booboo1]

Thanks guys
I used 145.6kohm as Rf and 2.14kohm as Rin and got an acceptable output. for example 70.1mv in the input, I got 4.93v in the output.

 

[otpowell]

MultiSim is my best friend when troubleshooting circuits like this. Just a suggestion.