There is no problem; it is not an OpAmp. You are expecting it to work like one...
By design, when both inputs are grounded, the output is supposed to sit at Vcc/2.
Hi Mike,
I think i understand how you can come to that conclusion, but i dont think i can agree with that. If we call vn the inverting terminal and vp the non inverting terminal for ease of notation, when vp=vn we have a 'no change' condition, where the output does not change one way or the other. So if it was 2v before than it is 2v after. We can have three conditions:
vp>vn, output ramps positively.
vp<vn, output ramps negatively.
vp=vn, output stays the same.
So in other words, when vp=vn we can show just about any output voltage is obtainable depending on the feedback and input to a standard amplifier circuit using an op amp for example.
Alternately, we might specify that when vp=vn we have 0v output, but then there is nothing to force that condition just like there is nothing to force the output to go to Vcc/2 either.
In the real life op amp however, when vp=vn externally, internally either vp>vn or vp<vn because of the small but significant input offset. In that case the output ramps according to
vp+voffset=vn
where voffset can be plus or minus. So the output either ramps up or down when externally vp=vn.
But a lot of times when someone says the input is at zero, they dont really mean the input to the op amp itself is zero but rather the input to the entire circuit is zero, such as when we have say an inverting amplifier with two resistors and the input is applied to the first resistor and the second resistor is the feedback. But yeah, a circuit schematic would help to clarify this which we'll have to wait for i guess