JPS5755603A - Power amplifier - Google Patents

Abstract

PURPOSE: To reduce notching distortion due to the turn-on time lag of trasistors (TR) by providing a constant current circuit and by operating the TRs in the active state all the time.

CONSTITUTION: An AC input signal is applied to the base of a TRQ₄ to be inverted by the TRQ in the positive half cycles of an input signal and power amplification is performed by TRs Q₈ and Q₁₀ to supply electric power to an SP as a load. In the negative half cycles, power amplification is performed by TRs Q₅, Q₆, Q₇, and Q₉ to supply electric power to the SP as the load. A constant current circuit composed of TRs Q₁₀₁, Q₁₀₂, and Q₁₀₃ and resistances R₁ and R₂ is provided to reduce notching distortion, thereby operating the TRs Q₅ and Q₇ in the active state all the time. Therefore, since the AC input signal is not intercepted by the TRs Q₅ and Q₇ during the periods of the positive half cycles, the notching distortion due to the turn-on time lag of the TRs Q₅ and Q₇ is improved remarkably when the input signal changes from the positive half cycle to the negative half cycle.

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