Designing a Low-Power LNA and Filter for Portable EEG Acquisition Applications

• Published in: IEEE access Vol. 9; pp. 71968 - 71978
• Main Authors: Moradi, Marzieh, Dousti, Massoud, Torkzadeh, Pooya
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplification; Amplifier design; Amplifiers; chopper-stabilized technique; Choppers (circuits); Circuits; CMOS; EEG; Electroencephalography; Fully recycling folded cascode amplifier; Gain; Gm-C filter; Low pass filters; low-noise design; Modulation; Noise; Power consumption; Recycling; Slew rate; Switches; Topology; Transistors
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2021.3076160

A circuit with a low-power low-noise amplifier and a Gm-C ultra-low-power filter is proposed in this paper for portable electroencephalogram (EEG) acquisition applications. The proposed circuit contains a two-stage chopper-stabilized fully recycling folded cascode (TSRFC) amplifier and a second-order continuous-time Gm-C low pass filter (LPF) with ultra-low-power consumption. The noise and input offset are reduced using the chopper-stabilized technique. A two-stage amplifier that consists of composite transistors and a recycling structure is proposed for the amplifier. Compared to a typical folded cascode CMOS amplifier, the proposed design has higher DC gain and slew rate as well as lower input-referred noise. This circuit has an adjustable second-order Gm-C LPF with very low power consumption. The amplifier achieves a midband gain of 70 dB and a −3dB bandwidth in the range 0.1-212 Hz. Moreover, the amplifier is designed in 0.18-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> CMOS process and the chip area of the proposed circuit with pads is <inline-formula> <tex-math notation="LaTeX">450\times 450\,\,\mu \text{m}^{2} </tex-math></inline-formula>. The adjustable LPF has a 100 Hz cut-off frequency. The proposed circuit has an input-referred noise of <inline-formula> <tex-math notation="LaTeX">0.7~\mu </tex-math></inline-formula>Vrms, (0.1 ~ 100Hz) and a power consumption of 380 nW at 1 V supply.