A −64.3 dB THD, 26 nV/√ Hz Bio-Potential Readout Analog-Front-End Amplifier With a Gm-C Integrator-Implanted DC Servo Loop, and a Bulk-Driven Ripple Reduction Loop
Kui Wen, Shubin Liu, Longjie Zhong, Yuke Shen, Zhangming Zhu
Abstract
This paper presents a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G_{m}$ </tex-math></inline-formula> -C integrator-implanted DC servo loop (GMCI2-DSL) and a bulk-driven ripple reduction loop (BD-RRL) for bio-potential readout analog-front-end (AFE) amplifier. The proposed bio-potential readout AFE amplifier employs the GMCI2-DSL and BD-RRL to achieve low noise and significant total harmonic distortion (THD) with small ripple amplitude. A prototype has been taped out using a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> standard CMOS technology, and the core circuit occupies 880 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}\,\,\times $ </tex-math></inline-formula> 630 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> . The mid-band gain is about 40 dB with a 1.3-V supply voltage, and the chip’s quiescent power is 10.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> . The measured results show that the input-referred noise density is 26 nV/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\surd $ </tex-math></inline-formula> Hz, and the input-referred integrated noise in the range from 0.5 Hz to 500 Hz is 0.93 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu V_{rms}$ </tex-math></inline-formula> . The measured THD of a 5- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}V_{pp}$ </tex-math></inline-formula> input sinusoidal signal at 5.1 Hz is −64.3 dB without any input offset. The amplitude of residue ripple is achieved as 197.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{V}$ </tex-math></inline-formula> around chopping frequency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{ch}$ </tex-math></inline-formula> ) by ripple suppression. High-fidelity and real-time electrocardiogram (ECG) signals are acquired.