I fear I cannot understand how this circuit provides temperature stabilization for Q2. My primal idea was that an increasing heat leads to increased collector currents, which will decrease the collector voltage at Q1 by a little and this will reduce both base currents and eventualy the collector current of Q2. Everything seems fine for now, but here comes the confusion: the reduced Ib1 will decrease Ic1 and Vc will be the same as before. I can understand that Ib1 is stable, duo to the clearly visual collector feedback, but what about Ib2? When Vc is back to normal(as it was before the variation in Hfe) i see no reason for Ib2 not to increase again. Apparently this one is missing something and he will be glad if someone helps him.
PS: please don't send me to other threads in this forum or in other forums, i've tried and nothing helps. It will be great if you can explain it here. Thanks!