{TAIL ~ The reference voltage Vref} is chosen equal to half the supply voltage to maximize the AC voltage swing of {HEAD ~ the output node} 
{ TAIL ~ The reference voltage Vref } is chosen equal to half the supply voltage to maximize the AC voltage swing of { HEAD ~ the output node }
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD