a gate electrode of said {TAIL ~ third N channel MOS transistor} receives {HEAD ~ a reference potential} at said second potential level 
a gate electrode of said { TAIL ~ third N channel MOS transistor } receives { HEAD ~ a reference potential } at said second potential level
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH