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