VMOS tube high-quality power amplifier circuit

The characteristic of this circuit shown is that it consists of a two-stage differential amplifier circuit, and the second-stage differential amplifier directly drives the power
amplifier output stage.
    VTi and VT2 form a differential input stage. The junction field effect transistor VT3 short-circuits the gate and source as a constant current source, and
RPi adjusts the constant current source current at work. 0-1.2mA (i.e. 0.5~0.6mA per tube).
    VT4 and VTs constitute the second-stage differential amplifier and drive circuit. R1l and Rl2 are the collector load resistors of VT and VTs.
Their resistance should be such that the voltage drop across them is less than the threshold voltage of the output tubes rr7-VT8. The function of VT6 is to make
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the working status of VT4 and VTs is as close to balance as possible.
    The voltage stabilizing tube VDi connected to the emitters of VT4 and VTs acts as a clamp. Its voltage stabilizing value
is determined by the voltage drop on the collector load resistor R3.R of the front-stage differential tube. This circuit uses 6V.
    Vr7 and VT8 are beam-level power amplifier output tubes, using V-MOS field effect tubes. Since the withstand voltage between the GS poles of the V- MOS tube
is generally only 30 to 40V, voltage regulator tubes VI and VI are added to protect the safety of its work. The voltage stabilization value of the voltage regulator tube
should be smaller than the gate-source withstand voltage value of Vr7 and VT8. Generally, 10~12V is enough.
    R13.R14 is designed to suppress the high-frequency self-excitation of the output tube. It can range from tens of klCl to 100klrr, and this circuit takes 33kr2.
    Ris~R17 and C4.c5 form a large loop negative feedback network. The closed-loop gain of the circuit is determined by the ratio of ruler 16/R17.