This presents a low-power fully differential optical sensor interface amplifier for photoplethysmography (PPG) and near infrared spectroscopy (NIRS) recordings. The proposed amplifier employs a stacked current reuse input stage that provides a DC biasing voltage for the photodiode, reducing the parasitic capacitance. The output stage exploits a fully differential current steering class AB topology with a self-regulated common mode voltage, providing a $70\mu \text{A}$ input current range with minimized quiescent current. Moreover, the interface amplifier can be reconfigured as either single-ended mode suitable for photo detectors biased at a high voltage or fully differential mode for those biased at a low voltage. This amplifier is implemented in a standard $0.18\mu \text{m}$ CMOS process and characterized experimentally. Measurement results show that, with a 1.5V supply, the amplifier can provide up to 1V biasing voltage for the photodiode and consumes a static power of around $50\mu \text{W}$ . It achieves a dynamic range of 97dB in fully differential mode with an input referred noise of 67pArms in 32Hz band and 102dB in single -ended mode with an input referred noise of 582pArms.

中文翻译：

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50μW 全差分接口放大器，具有用于 PPG 和 NIRS 记录的电流控制 AB 类输出级

这提出了一种用于光电容积描记 (PPG) 和近红外光谱 (NIRS) 记录的低功率全差分光学传感器接口放大器。建议的放大器采用堆叠电流重用输入级，为光电二极管提供直流偏置电压，从而降低寄生电容。输出级采用具有自调节共模电压的全差分电流控制 AB 类拓扑，提供 $70\mu\text{A}$ 具有最小静态电流的输入电流范围。此外，接口放大器可以重新配置为适用于偏压高电压的光电检测器的单端模式或偏压低电压的全差分模式。该放大器以标准实现 $0.18\mu\text{m}$ CMOS 工艺和实验表征。测量结果表明，在 1.5V 电源下，放大器可为光电二极管提供高达 1V 的偏置电压，并消耗约 $50\mu\text{W}$ . 它在全差分模式下实现了 97dB 的动态范围，在 32Hz 频段输入参考噪声为 67pArms，在单端模式下实现了 102dB，输入参考噪声为 582pArms。