What OPamp to use?

[IvoS]

I have MC33272 OPamp http://www.onsemi.com/pub_link/Collateral/MC33272A-D.PDF
I was thinking that when given the relatively low input offset around 0.1mV I would be able to have the output voltage at 0V or close to 0V (few mV) when positive pin is either grounded or connected to ground through a 10k resistor lets say. When I short both + and - input pins together or connect the positive pin to ground as I wrote, I still have  0.154V on the output. Question: Is there a way to have the output voltage close to 0 V with this OPamp? If not, what other OPamp should I be looking at? I was using single +12VDC supply to power this OPamp chip.

[w2aew]

The output voltage of 154mV really doesn't have anything to do with the input offset voltage.  It is due to the fact that your are using it in a single supply application, and the output stage can't get closer than that to the negative rail. The specs say that the output will be 200mV or less in a 5V single supply application with a 2K load.  You're stuck with the saturation voltage of the lower NPN output device, can't get closer to the negative rail than that.  If you want to get closer to GND, you'll have to use a negative supply rail that is below ground.

[SeanB]

You need an opamp that is true rail to rail on both input and output. The old LM324 can do ground on the inputs( actually it will go to -0.6V happily, but caveat emptor there), and will get close to ground if you use a pull down resistor on the output to actively pull it down( it then has an output stage that runs happily in class A as a current source). Will not go to 0V exactly, but will do well depending on the load. otherwise you do need a negative supply, anything more than about 2V will do, as the internal transistors need some voltage across them.

[IvoS]

OK, thanks guys.

[IvoS]

Wow   The actual MC33272 I was tested was defective. It's a dual OP amp, the second amp. pins 5,6,7 didn't work properly, couldn't make a comparator of it. What are the chances you buy 2 chips and one of them is faulty?... Mouser was the supplier here.