And if Vc is initially too low, then {TAIL ~ less current} would flow through Q2 to increase {HEAD ~ Vc} 
And if Vc is initially too low , then { TAIL ~ less current } would flow through Q2 to increase { HEAD ~ Vc }
OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD