At the non inverting input, {HEAD ~ a reference voltage Vref} is applied thru {TAIL ~ a resistor Rx} 
is applied thru
At the non inverting input , { HEAD ~ a reference voltage Vref } is applied thru { TAIL ~ a resistor Rx }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL