{TAIL ~ The reference voltage Vref} defines the DC level of {HEAD ~ both the virtual ground} and the output node 
{ TAIL ~ The reference voltage Vref } defines the DC level of { HEAD ~ both the virtual ground } and the output node
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH