The operational amplifier also includes source transistors for pushing {HEAD ~ the output and sink transistors} for pulling {TAIL ~ the output} to obtain particular output voltage swing 
for pulling
The operational amplifier also includes source transistors for pushing { HEAD ~ the output and sink transistors } for pulling { TAIL ~ the output } to obtain particular output voltage swing
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH