A highly sensitive wide-range weak current detection circuit for implantable glucose monitoring

A highly sensitive weak current detection circuit for implantable glucose monitoring is presented. The circuit consists of a current splitter, an integrator, a sampling/holding (S/H) circuit, and an 8-bit successive approximation register (SAR) analog-to-digital convertor (ADC). T-switches, source voltage shifting and correlated double sampling (CDS) technology are adopted to reduce the effects of leakage currents, charge injection, dc offset and low-frequency 1/f noise. The work range is divided into 5 sub-ranges to reduce the complexity and power consumption of current detection. The chip was fabricated with 0.13 μm CMOS technology. Test results show that the circuit can detect weak signal from 10 fA to 1 nA with 1.5V supply and 7.2 μW power consumption. The tested leakage current of the design is 4 fA.