Complementary differential fully symmetrical power amplifier 02

The circuit of this machine is shown in Figure 4-7. The input stage uses a complementary differential circuit. On the one hand, it can give full play to
the advantage of the differential circuit’s high common-mode rejection ratio. At the same time, the use of complementary push-pull can reduce nonlinear distortion. Increase dynamic range. The emitters of the four differential tubes
are respectively connected to negative feedback resistors, which can reduce the distortion of this stage. Transistors VT5 and VT6 are used for constant current. VT7 and VT8 form a
driving stage. The emitter resistor also plays a role in stabilizing gain and improving linearity. 6. Capacitor C3.C4 can prevent high-frequency self-excitation
.
    Transistors VT9 ~ VT14 form a cross-coupled push-pull circuit. Its biggest feature is that the working point does not require debugging of the final stage.
The tube automatically stabilizes in the Class A and Class B working conditions. The common cross-coupling circuit is shown in Figure 4-8(a). It is only suitable for applications with
large load impedance. stage, otherwise the dynamic range will be reduced. The first solution is to add a bootstrap circuit, as shown in Figure 4-8(b). However,
the disadvantages are that the excitation tube consumes a lot of power, the amplifier power efficiency is low, and the transient effect changes I. The second is to add a Diodes and a low-
power excitation tube can overcome the shortcomings of the first method.
    The third feature of this circuit is the large loop feedback circuit. The first is to use 100% DC negative feedback to ensure that
the DC voltage at the output end is OVo after power is turned on. R5 is connected to t to ensure that the voltage is also OVo when the output end is not connected to a speaker. Secondly, the feedback signal is
fed back by the voltage (through R3.R2 .Rl) and current feedback (through R6.R4.RZ). The addition of the latter can also reduce the nonlinear
distortion of the speaker and make the sound of this unit more pleasant. The function of C6 is to provide advance compensation, which can increase operating stability and further reduce transient intermodulation distortion.