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