At static, because the parameters of the two tubes are consistent, the input (point B) and output (point A) voltage in the circuit are half of the power supply voltage, at this time, the emitter voltage of V and V=V-V=0, and both tubes are cut off.
When the input AC signal V is positive half-cycle, the NPN tube V is switched on and the PNP tube V is cut off due to the increase of the triode base potential, and the power supply V is charged to the coupling capacitor C through V, and the positive half-cycle waveform is output on the load plate.
When the input AC signal V is negative half cycle, because the triode base potential drops, the V tube shuts off the V tube, the coupling capacitor V discharge provides power to the V tube, and outputs the negative half cycle waveform on the load. It must be noted that when V is negative for half a week, the V tube is cut off, so that the power supply V cannot continue to supply power to V. At this time, the coupling capacitor C uses the electric energy charged by it to supply power to the V tube instead of the power supply. Although the capacitor C is sometimes charged and sometimes discharged, the capacity is large enough, so the voltage at both ends is basically maintained at V2.