| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an amplifier capable of reducing distortion in an output signal caused by impedance mismatch, depending on the number of transistors that are turned ON in a switching amplifier. <P>SOLUTION: An amplifier modulates an input signal into a discrete signal by a ΔΣ modulator, and amplifies the discrete signal by a switching amplifier. The ΔΣ modulator has a quantizer whose output value p and threshold x can be controlled. The switching amplifier has a plurality of transistors switched depending on the discrete signal, a transformer that synthesizes output signals from the transistors, a matching circuit connected to an output side of the transformer, and a power detector that detects a power value in an output power between the matching circuit and a load Rload. Further the amplifier has a controller that changes the number N of the transistors that are turned ON to control the switching for the switching amplifier, inputs a power value P from the power detector, and sets an output value q and a threshold x of the quantizer in the ΔΣ modulator depending on the power value P. <P>COPYRIGHT: (C)2012,JPO&INPIT |
