Analysis of self-retained feedback of OCL power amplifier

The working principle of DC feedback is shown in Figure 1-31. In the circuit,
R7 is connected between the output terminal (midpoint when static) D and
the base of the differential input stage Vr. For static purposes, this is a full negative feedback circuit,
that is, a voltage follower . Its voltage amplification factor is 1. The output voltage
follows the change of the input voltage. As analyzed before, Vbl=VbZ=ov,
so the midpoint voltage VD= OV oWhen VD rises for some reason,
through the adjustment effect of negative feedback, VD will be automatically returned to
ovo