SWITCHING TYPE ALTERNATING-CURRENT SIGNAL AMPLIFIER

摘要

PROBLEM TO BE SOLVED: To suppress increases in the output capacity, size, and cost of a switching type AC signal amplifier. SOLUTION: An adding circuit 2 adds the input voltage Vin inputted from an AC signal source 10 to the switching type AC signal amplifier 1 to a feedback voltage Vfb and a pulse-width modulating circuit 4 converts the added signal Va into a switching signal Vs. An inverter circuit 5 amplifies the electric power of the signal Vs and an output voltage Vout is outputted through a filter 7. The output current Iout of the inverter circuit is detected by a current detecting circuit 6 and converted into a voltage signal Vfb by a current/voltage converting circuit 8 which has a feedback coefficient and forms a feedback circuit. Here, the output impedance of the amplifier viewed from the amplifier and an output terminal is equal to the feedback coefficient and held constant even if the output current Iout or the AC signal inputted from the output terminal vary owing to the variation of a load 11, so that the above output impedance functions as active output impedance.