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