Two-stage difference amplifier OCL amplifier

The principle of power amplifier circuit is shown in Figure 2.60. From the structure of the circuit, it can be seen that it is a relatively typical OCL power amplifier circuit .
The actual working performance is very good and it is a better power amplifier circuit structure.
    The input part of the circuit is composed of C1.Ri as a high-pass filter. R3 has formed a low-pass filter - its purpose is to limit
the effective bandwidth of the input, attenuate ultra-low frequencies, and reduce transient mutual distortion.
    VTz and VT3 form a differential input stage, and VTi is its constant current source, VI) 1. , VI jade is the base bias voltage reference of the constant current source
. R7 and R are the collector load resistors of VT2 and VT3, and also serve as the base bias of the second-stage differential circuit VT4 and VTs
.
    VT4 and VTs form the second-stage differential amplifier circuit for voltage amplification. VT6 and VI are used as the mirror constant current detection load of the second differential amplifier
. Here, diode VI Ga is used as the mirror constant current tube instead of short-circuiting the collector. triode, but its
working principle is the same.
    , r6 is used as the voltage driving stage of the output stage, and at the same time, it turns the differential circuit into a single-ended output.
    VTio.Vrll forms a fully complementary symmetrical push-pull power output NPN composite tube, and VT12.VT13 forms a PNP composite
tube.
    VT7. , RPi and R5 form the bias circuit of the output stage o