the second power supply supplies a second power supply voltage obtained by adding a voltage corresponding to a forward voltage drop of {HEAD ~ the second and fourth diodes} to {TAIL ~ the second predetermined voltage} 
to
the second power supply supplies a second power supply voltage obtained by adding a voltage corresponding to a forward voltage drop of { HEAD ~ the second and fourth diodes } to { TAIL ~ the second predetermined voltage }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL