A Low-Power Wide Dynamic-Range Current Readout Circuit for Ion-Sensitive FET Sensors

This paper presents an amplifier-less and digital-intensive current-to-digital converter for ion-sensitive FET sensors. Capacitance on the input node is utilized as a residue accumulator, and a clocked comparator is followed for quantization. Without any continuous-time feedback circuit, the converter performs a first-order noise shaping of the quantization error. In order to minimize static power consumption, the proposed circuit employs a single-ended current-steering digital-to-analog converter which flows only the same current as the input. By adopting a switching noise averaging algorithm, our dynamic element matching not only mitigates mismatch of current sources in the current-steering DAC, but also makes the effect of dynamic switching noise become an input-independent constant. The implemented circuit in 0.35 ��m CMOS converts the current input with a range of 2.8 �� A to 15 b digital output in about 4 ms, showing a DNL of +0.24/-0.25 LSB and an INL of +1.98/-1.98LSB while consuming 16.8 ��W. ? 2007-2012 IEEE.113sciescopu

Wide Dynamic Range, Highly Accurate, Low Power CMOS Potentiostat for Electrochemical Sensing Applications

Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting low-level sensor current, the performance of potentiostat linearity which causes the detectable current and dynamic range to be limited is relatively decreased. Thus, to alleviate these irregularitiesthe designed with a wide output voltage swing were implemented using TSMC 0.18-μm CMOS process for biomedical application. Measurement results show that the fully differential potentiostat performs relatively better in terms of linearity when measuring current from 100 pA to 60 uA