While building an opamp based non-inverting amplifier for my project I noticed that it always has some considerable output voltage despite having the input at zero. To verify that problem I built the following simple test circuit:
I would imagine that the output voltage of this circuit would be very close to zero, however it's about 5 mV. According to the datasheet of OPA189 the input offset is only 3 uV, so not sure why am I getting 5mV output considering so low gain of only 2? In fact based on my tests, the output offset voltage doesn't even depend on the gain value. I tested another op amp ADA4522, and this one has similar problem with more than 7 mV output offset. Could anyone give me pointers on why this could be happening and what can be done to lower the output offset to 1 mV or less? Thanks!