POWER AMPLIFIER

PURPOSE:To realize low noise and high efficiency of an amplifier by connecting an audio signal in opposite phase and a carrier signal in phase, a balanced transformerless (BTL) fashion and connecting a capacitor in parallel with a load. CONSTITUTION:In extracting a pulse signal subjected to power amplification via a low-pass filter 5, a low frequency output signal similar to an audio input signal from which a signal component corresponding to a carrier signal is eliminated is fed to one terminal of the load. In extracting the signal via a low-pass filter 5', since the signal passes through an inverting circuit 8, the low frequency output signal of opposite phase is fed to the other terminal of the load. That is, because of BTL connection, a low frequency signal having a double output voltage is extracted across the load. Then the signal through the low-pass filters 5, 5' is fed back to preamplifier circuits 1, 1' via feedback circuits 6, 6'. Further, a leaked carrier signal component after the low-pass filters 5, 5' is cut off by a capacitor 9 connected in parallel with the load 7.