Analysis and Design of Tunable Amplifiers for Implantable Neural Recording Applications

In this paper, an in-depth design methodology for fully-integrated tunable low-noise amplifiers for neural recording applications is presented. In this methodology, a modified system design is proposed to optimize the area/noise/linearity performance. A novel linear pseudo-resistor with a wide range of tunability is also proposed. As a case study, a low-noise tunable and reconfigurable amplifier for neural recording applications is designed and simulated in a 0.18 $\mu{\rm m}$ complementary metal–oxide–semiconductor process in all process corners. Simulated characteristics of the amplifier include tunable gain of 54 dB, tunable high-cutoff frequency of 10 kHz, programmable low-cutoff frequency ranging from 4 to 300 Hz, and power consumption of 20.8 $\mu{\rm W}$ at 1.8 V. According to postlayout simulations, integrated input-referred noise of the amplifier is 2.6 $\mu{\rm V}_{\rm \rms}$ and 2.38 $\mu{\rm V}_{\rm \rms}$ over the 0.5 Hz–50 kHz frequency range for low-cutoff frequency of 4 and 300 Hz, respectively. The amplifier also provides output voltage swing of 1 ${\rm V}_{\rm P-P}$ with total harmonic distortion of -46.24 dB at 300 Hz, and -45.97 dB at 10 kHz.