Composite complementary symmetrical push-pull output stage circuit

The complex complementary symmetrical push-pull output stage circuit is shown in the figure. In the figure, vri, VD1, VD2 and R constitute the push stage. VT2 and
VT3 are compositely connected to form an equivalent NPN tube, and VT4, VT5 and VT6 form an equivalent PNP tube. The tube type of the latter
is determined by the horizontal PNP tube (VT4), and its equivalent total current amplification coefficient is: f= f/4 (1+p5)(l+p6)-f/4. pi L86. During the manufacturing process, control
p4 of the transverse PNP tube so that p4=1, then Lukou 5. Nose 6. VT5 and VT6 are both NPN tubes, and their characteristics and parameters can be the
same as VI2 and VT3. In this way, a pair of composite complementary NPN tubes and PNP tubes with very similar characteristics can be obtained.
    In order to reduce the crossover distortion, the forward voltage drop of the diodes VD1 and VD2 ( a transistor that short-circuits the c and b poles ) is used to provide an appropriate bias voltage for the output stage
, so that it works in a Class A and B state close to Class B. VD1 and VD2 also have temperature compensation function. R is the collector
DC load resistor of VT1 .