a fourth switching element disposed between a control terminal of {TAIL ~ the first switching element} and {HEAD ~ a control terminal} of the third switching element 
a fourth switching element disposed between a control terminal of { TAIL ~ the first switching element } and { HEAD ~ a control terminal } of the third switching element
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH