Sawashi, Tokihiko;

Power amplifier apparatus

A power amplifier apparatus includes a pair of power amplifiers for performing switching-type power amplification, a transformer, and a capacitor. The transformer is formed of a pair of coils that are connected in series between the corresponding output terminals of the pair of power amplifiers and the corresponding terminals of a speaker. The capacitor is connected in parallel with the output terminals of the pair of coils. With this configuration, a mutual inductance and a leakage inductance are generated in the coils. As a result, 180.degree. out-of-phase and in-phase noise components contained in an output of the power amplifier apparatus can be eliminated.

What is claimed is:

1. A power amplifier apparatus comprising:

a pair of power amplifiers connected to form a balanced-transformerless-type amplifier for performing switching-type power amplification;

a transformer including a pair of coils connected in series between output terminals of said pair of power amplifiers and corresponding input terminals of a speaker; and

a capacitor connected in parallel with output terminals of said pair of coils,

wherein said pair of coils include a mutual inductance and a leakage inductance for altering signals fed through said pair of coils.

2. The power amplifier apparatus according to claim 1, further comprising a drive amplifier for supplying pulse modulation signals to said pair of power amplifiers, wherein the pulse modulation signals are out of phase with each other by 180 degrees and an integrated value of the pulse modulation signals corresponds to a level of an original analog audio signal fed to said pair of power amplifiers.

3. The power amplifier apparatus according to claim 1, wherein said transformer comprises a separated-type transformer in which said pair of coils are wound around corresponding independent cores.