The basic idea of how the two-stage feedback works: Assume that an increase in temperature causes the output voltage to increase. Since the part of the output voltage is fed back to the emitter, ve increases. This decreases vbe in the first stage, decreases ve in the first stage, and decreases vout. On the other hand, if the output voltage tries to decrease, vbe increases and v out increases again.
In either case, any attempted change in the output voltage is fed back and the amplified change opposes the original change. The overall effect is that the output voltage will change by a much smaller amount than it would without the negative feedback. The voltage gain is:
Av = rf/re + 1
