High voltage OP amplifier circuit analize
Q1 runs as Pchannel common-gate, pulling up on gate of the Q2 Nchannel with source at -180 volts. 

U1,Q1,Q2 are a non-inverting feedback loop. If my words: Q1 is Pch, Q2 is Nch, are correct. Thus only Q2, wired common-source, is inverting and no Schmitt action occurs. Is OpAmp (+) sign properly located?

Predict the current? by assuming Von of Q3 is zero volts, thus all the zener voltage is across R12 the 5Kohm in the source. Current is 10v/5Kohm = 2mA.