Shin Young-San, Lee Seongsoo, Wee Jae-Kyung, Song Inchae
School of Electronic Engineering, Soongsil University, Seoul 156-743, Korea.
IEEE Trans Biomed Circuits Syst. 2013 Jun;7(3):276-84. doi: 10.1109/TBCAS.2012.2212018.
In this paper, a small-area and low-power current readout circuit with a novel two-stage conversion method is presented for 64-channel CNT (carbon nanotube) sensor arrays. In the first stage, current of each CNT sensor is amplified by 64 active input current mirrors (AICMs). In the second stage, the amplified current is converted to a voltage level through the shared variable gain amplifier (S-VGA). Then the S-VGA output is digitalized by successive approximation register analog-to-digital converter (SAR-ADC). The proposed readout circuit significantly reduces chip area and power consumption, since VGA is shared over 64 channels and passive elements are used only in S-VGA. Fabricated chip area is 0.173 mm(2) in 0.13 μm CMOS technology. Measured power consumption and linearity error are 73.06 μW and 5.3%, respectively, at the input current range of 10 nA-10 μA and conversion rate of 640 samples/s. A prototype real-time CNT sensor system was implemented using the fabricated readout circuit, and successfully detected alcohol reaction.
本文针对64通道碳纳米管（CNT）传感器阵列，提出了一种采用新型两级转换方法的小面积、低功耗电流读出电路。在第一级，每个CNT传感器的电流由64个有源输入电流镜（AICM）进行放大。在第二级，放大后的电流通过共享可变增益放大器（S-VGA）转换为电压电平。然后，S-VGA的输出由逐次逼近寄存器模数转换器（SAR-ADC）进行数字化。由于VGA在64个通道上共享且仅在S-VGA中使用无源元件，因此所提出的读出电路显著减小了芯片面积并降低了功耗。采用0.13μm CMOS工艺制造的芯片面积为0.173mm²。在输入电流范围为10nA至10μA且转换速率为640样本/秒的情况下，测得的功耗和线性误差分别为73.06μW和5.3%。利用所制造的读出电路实现了一个原型实时CNT传感器系统，并成功检测到了酒精反应。
