| 摘要 |
In a digital amplifier of the PCM-UPWM type there is no negative feedback stage, which means that noise caused by the switching output stage of such an amplifier is directly affecting the audio signal. According to the invention, a regulation loop is inserted between the output and the input of the digital amplifier, said regulation loop being adapted to form a compensation signal c(k) which is multiplied by the audio signal to compensate noise and errors from the switching output stage. In an embodiment, the regulation loop consists of a multiplying D/A converter (2) which is adapted to multiply the compensation signal c(k) by a multiplicative error signal m(t), and a summation unit (3), by summation of the output of the multiplying D/A converter (2) and a reference voltage (6), forms a second error signal e(t) which is fed to a low-pass filter (4) that is fed to the input of an ADC circuit (5) to form the multiplicative error signal c(k), which, optionally via a second adaptation filter (21), is fed to a multiplier (11) and the multiplying D/A converter (2). Expediently, the circuit of the invention is formed in full or in part by an integrated circuit.
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