Integrated circuit BTL amplifier 03

The key to reducing open-loop distortion in a power amplifier circuit is that both the circuit form and working state must be symmetrically balanced. Integrated circuits
form BTI power amplifiers to make the output circuit more symmetrical. As shown in Figure 5-49, the BTL emergency circuit port outputs a positive half-cycle current
b flowing through Vl, RI, and V4; a negative half-cycle current b flowing through V3, RL, and V2. The ideal situation is that the current b flows through V3, RL, and V2 in each cycle. R and b of RI
are equal in value and opposite in direction. A symmetrical and complete sine waveform is synthesized on RI. The condition is:一&, &
=and, or pl=口. , &= wind, the circuit can obtain the symmetrical output of la -Ib. As we all know, the final stage of many audio integrated power discharge
circuits uses a quasi-complementary single-ended push-pull circuit. The two same-polarity tubes at the final stage of this circuit are not in the same working
configuration (common emitter and common collector hybrid). Although the tubes The parameters are very close to the same, but the working status of the upper and lower arms is asymmetric, so
the open-loop distortion is very large. Its high index output is obtained by deep negative feedback, which also contains potentially large transient intermodulation distortion
. If it is formed into a BTL circuit, this asymmetric state can be greatly improved. Especially two-channel integrated circuits
(such as STK465, etc.) inherently have 8, 1, &= and good symmetry. After forming a BTL circuit, it is easy to obtain
saddle-low open-loop distortion, and its output is high. The indicator is the real good indicator, and the sound quality can be significantly improved. For mono
integrated circuits, due to the better consistency of the tube parameters in the integrated circuit , when two mono circuits form
a BTL circuit, It is also easier to satisfy B. =p:,p. =p4 symmetry condition, and obtain lower open-loop distortion.