a fourth N channel MOS transistor connected between {HEAD ~ the other conductive terminal} of said fourth P channel MOS transistor and {TAIL ~ the ground potential}, and 
a fourth N channel MOS transistor connected between { HEAD ~ the other conductive terminal } of said fourth P channel MOS transistor and { TAIL ~ the ground potential } , and
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH