At the inverting input of the operational amplifier Ao a virtual ground is created by {HEAD ~ means} of feedback from {TAIL ~ the output node Vout} through feedback resistor Rfb 
At the inverting input of the operational amplifier Ao a virtual ground is created by { HEAD ~ means } of feedback from { TAIL ~ the output node Vout } through feedback resistor Rfb
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH