Attached is a bias circuit, would like to discuss what the function of Q176 and Q174. In my opinion, when CD(chip disable) level is high, Vref is set to zero, and then Q172 and Q178 are cut off, so Q176 and Q174 and R85 form a Wildar current souce and supply current to Q170, so as to make sure Vref is set to zero.
ok, i think i understand. If the circuit works at the zero balance point, then Q174 will drive current from Q147, and the current is mirrored to Q143, and the working point will come to the normal point that we want.