Check that this produces what you think it should, with 0V on the bottom "leg" (ie the bottom end of the resistor attached to the inverting input to the Op-Amp). Now increase or decrease that voltage from 0V. What happens?
Basics of Electronics ... a "Toybox" by Alan Murray, University of Edinburgh is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.