| Citation: |
Li Fanyang, Yang Haigang, Liu Fei, Yin Tao. A current mode feed-forward gain control system for a 0.8 V CMOS hearing aid[J]. Journal of Semiconductors, 2011, 32(6): 065010. doi: 10.1088/1674-4926/32/6/065010
Li F Y, Yang H G, Liu F, Yin T. A current mode feed-forward gain control system for a 0.8 V CMOS hearing aid[J]. J. Semicond., 2011, 32(6): 065010. doi: 10.1088/1674-4926/32/6/065010.
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A current mode feed-forward gain control system for a 0.8 V CMOS hearing aid
doi: 10.1088/1674-4926/32/6/065010
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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 0.13 μm 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 40 μW. In addition, the input referred noise is only 4 μVrms and the maximum gain is maintained at 33 dB.-
Keywords:
- current mode,
- gain control,
- hearing aid
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