80W power amplifier circuit

This is a power amplifier circuit using NE5534 as the pre-stage . Like NE5532, NE5534 is also a high- performance operational amplifier circuit. The difference between them is that NE5534 is a single op amp and adopts the structure of external compensation and external zero adjustment, which is more convenient to use. The l-8 pins of NE5534 are directly connected to the 100mm potentiometer for zero adjustment, and the 5-8 pins are indirectly connected to the external compensation capacitor. According to the requirements, its capacitance range should be between 5~20pF. If the circuit design is good and there is no self-excitation, it can be omitted. When external connection is required, the maximum capacity should not be greater than 20pFo     Circuit Blood II Figure 2-117. The power supply of NE5534 adopts the power supply method of resistor voltage reduction, voltage regulator tube voltage stabilization and resistor-capacitance 7c type wave filtering. The power supply voltage is ±15Vo. In addition to the large-capacity electrolytic capacitors C5 and C7, there is also a small- capacity power supply filter capacitor. Capacitor C3 is used to filter out high-frequency interference pulses in the power supply and obtain pure DC working power.     VTl and VTz form the output push stage. As can be seen from the figure, they are connected into a common emitter circuit, so they have voltage amplification capabilities. This connection method can make up for the shortcomings of the small output voltage of the op amp.     VT3 and VT4 are A complementary push-pull output stage composed of field effect transistors. Since the field effect transistor is a voltage-driven amplifier device and has smaller requirements for driving current, it is more adaptable to the characteristics of this circuit and can output greater power. .     R3, R2, and c2 form the feedback loop of this circuit.     The output power of this circuit can reach 80W under the working power supply of ±45V. If IRF150 and IRF9150 are used as output tubes, the output power will increase.