High dynamic, low distortion all-crystal triode three-stage differential power amplifier

This circuit uses all transistors in order to overcome the shortcomings of the above two circuits. Three-stage
differential amplification is used to reduce the distortion of the power amplifier. We already know that the relationship between the output and input of the closed-loop amplifier circuit is:
    i1-
    KKoFF1 Stool (1-RoF J)
In the formula, Ux and Ut are the output and input voltages respectively. RA and RB are shown in Figure 4-¨. The negative feedback resistor, F is the voltage feedback
coefficient, and Ko is the open-loop amplification factor.
    It can be seen from the formula : When the open-loop amplification factor K. is larger, the l/KoF term is smaller, and the ratio of Ux to U$r U c/U,.r term is close to
the R^/RB term, which means the distortion is smaller. Therefore, When the amplification factor of each stage is the same, the distortion rate of a three-stage difference amplifier is much smaller than that of a power amplifier
with only one or two stages .     In order to eliminate the transient distortion under deep feedback, this circuit uses In order to form a low-pass filter network formed in the dotted box in the figure and connect a locl1 resistor between the input terminal and the circuit ground (ov), the off-state distortion is effectively suppressed. When the circuit outputs low, the distortion The frequency is less than 0.ooz%, the intermodulation distortion is less than 0.003%, and the frequency response is 10Hz~ 68kHz.