Power dissipation of bioamplifiers has become one of the most critical factors for up-to-date implantable neural recording microsystems as the increasing of recording channels. This paper presents an ultra-low-power bioamplifier which is designed for the very-large-scale integration of neural recordings. To reduce the power, the proposed bioamplifier is designed to work with a 0.5 V power supply and all MOSFETs operate at weak inversion region. Both folded-cascode and wide-swing structures are employed to fully exploit the output swing. By producing a 18∶1 bias current ratio between input transistors and load current mirror, the noise performance of the proposed bioamplifier is optimized for the given power dissipation. Designed in a 0.13-µm CMOS process, the proposed bioamplifier consumes only 61.7 nW power to obtain a gain of 23.8 dB and a bandwidth of 3.6 KHz. The input-referred noise over the entire bandwidth is 12.7 µVrms, corresponding to a noise-efficiency factor of 3.1.
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