Single supply complementary symmetrical circuit

Shown is a single-supply complementary symmetrical circuit, referred to as an "OTL" circuit (which means a power amplifier circuit without a transformer).
The complementary symmetrical OTL power amplifier uses two transistors with opposite conduction polarities , so it only requires the same base signal turn
.
    In the figure, transistor VT2 is an NPN transistor. V13 is a chat transistor. The push stage\rricollector output voltage Ucl is
the base signal voltage of VI2 and VT3. The collector resistors R3 and R4 of VT1 also provide base bias voltages for VT2 and VT3, making them work
in an amplified state. Capacitor C4 is connected between the output terminal and the load to block DC and pass AC. Due to charging
, there is a DC voltage uC4-UCCt2 (charged) at both ends of the capacitor C4 , so it is also the DC power supply of the VT3 tube.
    The input signal Ui is coupled to the base of transistor VT1 through capacitor C1, and is amplified by VT1 into signal Ucl. During the positive half cycle of the signal Uq,
VT2 is turned on, VT3 is turned off, and the amplified current Iol is output; when the signal Uc. During the negative half cycle, VT3 is turned on. VT2 is cut off, and the amplified current is output
as an island. The output amplified signal is synthesized into a complete signal waveform on the speaker through the output coupling capacitor C4.
    In a single-supply complementary symmetrical circuit , the operating voltage of each triode is not Ucc, but Ucc/2.