car stereo power amplifier

Shown is a car stereo power amplifier circuit, in which the output transistors VT3 and VT4 adopt a mutually symmetrical connection method. The output
signal is supplied to RL via bulk coupling capacitor C4. VT2 is designed according to the function of a Class A power amplifier , and voltage amplification is performed at this stage. The collector current
of VT3 and VT4 is more than 100 mA, and the base current is more than 10 mA. The collector circuit of Yr2 is also the base bias circuit of VT3 and VT4. It provides static base current for VT3 and VT4 , so. , The load resistor of rr2 is limited by the power supply voltage and has a low resistance value, so it cannot obtain sufficient voltage gain. The island is a bootstrap capacitor, and the output voltage is boosted through c3 at the contact point of V12's load resistor Fan and Rg . The stronger the signal, the higher the boost amplitude, thus increasing the amplitude of the output signal while continuously increasing the power supply voltage.