A current mode feed-forward gain control system for a 0.8 V CMOS hearing aid |
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Authors: | Li Fanyang Yang Haigang Liu Fei Yin Tao |
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Affiliation: | 1. Institute of Electronics,Chinese Academy of Sciences,Beijing 100080,China;Graduate University of the Chinese Academy of Sciences,Beijing 100049,China 2. Institute of Electronics,Chinese Academy of Sciences,Beijing 100080,China |
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Abstract: | A current mode feed-forward gain control (CMFGC) technique is presented, which is applied in the front-end system of a hearing aid chip. Compared with conventional automatic gain control (AGC), CMFGC significantly improves the total harmonic distortion (THD) by digital gain control. To attain the digital gain control codes according to the extremely weak output signal from the microphone, a rectifier and a state controller implemented in current mode are proposed. A prototype chip has been designed based on a 0.13μm standard CMOS process. The measurement results show that the supply voltage can be as low as 0.6 V. And with the 0.8 V supply voltage, the THD is improved and below 0.06% (-64 dB) at the output level of 500 mVp-p, yet the power consumption is limited to 40μrms. In addition, the input referred noise is only 4μVrms and the maximum gain is maintained at 33 dB. |
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Keywords: | current mode gain control hearing aid |
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