XA8500 power amplifier

The XA8500 amplifier won the two awards of "Most Rated Product" and "Most Loved Product" at the first domestic audio equipment exhibition
. Its circuit is carefully designed and assembled using high-quality Nissan transistors.
    The circuit principle is shown in Figure 2-10. It is composed of It consists of three parts: a dual differential input stage, a voltage amplification stage and a power output stage.
    VTi ~ VT6 form a fully symmetrical complementary dual differential input stage, VT3 and VT6 are the constant voltages of each pair of differential circuits respectively .
Source port
    VT7 ~ VTi: form a complementary Symmetrical push-pull voltage amplifier stage, Vding7, VT8 and VTio, v, rl1 form a common-emitter
and common- base amplifier circuit, VTg and VT12 form a constant current source base bias circuit. Common-emitter-Hong base circuit is also Called the Holman circuit
, it is an amplifier circuit with excellent linearity . This circuit can not only improve the linearity of the circuit, but also broaden the frequency band.
Many new power amplifiers use this circuit.
    It is determined by the output characteristic curve of the transistor It can be seen that the output of the transistor has better linearity when y ce is constant, but
the Vce of the common emitter amplifier changes with the change of the output current, which prevents the upper and lower half cycles of the output waveform from receiving the same
amplification. The cascode circuit that causes the distortion of the output waveform has the characteristic of making V-chip unchanged, thus
maintaining good linearity of the V value and improving the linearity of the circuit .