70W power amplifier circuit

The operational amplifier stage of this circuit adopts the transistor voltage stabilization power supply method, and the voltage regulator tube provides the reference voltage
, and the power supply voltage is ±15V.
    In the output stage of this circuit, in addition to the normal connection to R13 and R14, the emitters of VT3 and VT4 are also connected to
R1l and R12, and the other ends of Rl 1 and RI2 are grounded. The output signals are output from the collectors of VT and VT4 respectively.
This means that due to the addition of Rj l and Rl2, VT and VT4 form a common-emitter amplifier circuit, which has a
certain voltage amplification capability. This circuit is designed for 7 times.
    Since the output stage has voltage amplification capability, the voltage output of the pre-stage does not need to be very high. This circuit requires that
the IC has an output voltage of 5v, which is 0 5V × 7-35V. In this way, the output power of the circuit can reach 70 Wo.
    The circuit adjustment is relatively simple. You only need to adjust the island and Rlo so that the final quiescent current is between l0 and 20mA.