As shown in the figure, this circuit uses an A1 (CA3100) integrated circuit as the input stage, while the power amplifier stage uses a separate transistor, which is actually two cascaded amplifier modules with a common feedback loop. The column amplification module is composed of R17, R10 and C8 to form its own local feedback. The input stage of the split section is a common base VT12, VT13 (Q12, Q13) circuit. This stage is used as a voltage converter and works in class A. The next stage VT1, VT2 (Q1, Q2) also works in class A And its main function is voltage amplification.
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