| 摘要 |
PURPOSE:To improve the linearity of a voltage amplifier stage to a load by detecting a collector current of a buffer transistor (TR) by a current mirror circuit and applying positive feeback to a base of the buffer TR relating to a power amplifier with low distortion factor for audio so as to increase apparently the hfe of the buffer TR. CONSTITUTION:In setting values of C1, C2, R11, R12 of a current mirror circuit so that the gain of a positive feedback loop consisting of TRs Q6, Q7 of single ended push-pull (SEPP) buffer, TRs Q8, Q9, capacitors C1, C2 and resistors R11, R12 is unity, the base current of the TRs Q6, Q7 is fed from the TRs Q8, Q9 in response to the collector current of the TRs Q6, Q7 and the input impedance of the TRs Q6, Q7 is inifinite apparently. Thus, the load of the TRQ1 is considered as the resistor R2 only and the gain of the TRQ1, is constant without being affected by the nonlinarity.
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