A weak current detection circuit with LDO for electrochemical sensors

Electrochemical sensors applied in single molecules detection can only trigger a weak pA-level current, which is hard to detect. In this paper, a weak current detection circuit with LDO for electrochemical sensors is presented to achieve high-precision measurement. A precision transimpedance amplifier with a novel Input bias current elimination technique is used to amplify the weak current. In addition, a stable electric potential difference to the electrodes of the sensor needs to be provided when the electrochemical sensors operate, so a novel low-power LDO was designed, which provides a 3.3 V stable voltage. The chip has been manufactured in a 0.35 μm BCD process and occupies an active chip area of 1.83 mm*2.10 mm. Experimental results confirm that the proposed TIA has an input bias current of maximum 93 fA. The circuit can detect the current signal from 2 pA to 7 nA. The input integrated noise current of the detection circuit is 0.23pArms. The LDO of the chip supplies an output voltage of 3.3 V and consumes 50 nA of quiescent current.