| 摘要 |
PROBLEM TO BE SOLVED: To provide a class D amplifier wherein interference in a radio frequency band is remarkably reduced, and an operating frequency of a pulse width modulator is held to be constant independently from an input voltage. SOLUTION: A hysteresis voltage supply source 42 is provided with a first differential amplifier 44, a second differential amplifier 46 and a multiplier 48. An input voltage Vi is connected to a (+) input terminal of the first differential amplifier 44 and a (-) input terminal of the second differential amplifier 46. Signals appearing on output terminals of the amplifies 44 and 46 are K(Vs+ Vi) and K(Vs-Vi), respectively, where K is the gain of the amplifiers 44 and 46. The signals are connected to two input terminals of the multiplier 48, which supplies a hysteresis voltage signal of K<2> (Vs-Vi)(Vs+Vi) to a window comparator 22. A saturable reactor for restraining an overcurrent in the case of switching is installed in a driving stage of an amplifier 32.
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