Amplifier clipping distortion indicator with adjustable supply dependence

摘要

A circuit and method are provided for generating a clipping distortion detector output signal for an integrated circuit audio amplifier which is independent of operating temperature and supply voltage. The system includes an audio amplifier having a voltage gain, a first input for receiving an input voltage and an output for generating an amplified output voltage. A supply voltage is supplied to the audio amplifier and the supply voltage determines the maximum amplified output voltage. A comparison voltage is generated which is indicative of the output voltage divided by the voltage gain. A clip detector voltage comparator receives the input voltage and the comparison voltage and provides a clipping distortion detect signal when the input voltage deviates from the comparison voltage in excess of an offset voltage which is indicative of detection of excessive clipping distortion. According to one embodiment, the offset voltage is adaptively controlled as a function of the supply voltage so as to maintain a substantially constant maximum percent distortion. According to a second embodiment, the offset voltage is adjusted as a function of supply voltage to achieve an adjustable maximum percent distortion. In addition, the offset voltage is also controlled as a function of temperature to provide temperature compensation. The supply voltage and temperature compensation may be achieved by generating a current source as a function of supply voltage and temperature.