Design and Implementation of Ultralow Current-Mode Amplifier for Biosensor Applications

Recently, along with the booming of research and production of a CMOS integrated biosensing system (IBS), the ultralow current-mode amplifier (ULCA), which serves for the preamplification of biosensor signals, has been in high demand in areas like ultralow biocurrent analysis and detection, deoxyribonucleic acid probing and surveying systems, etc. In this brief, a novel ULCA is presented and implemented in SMIC 0.18- mum CMOS technology by elaborately considering gain, bandwidth, noise, and offset issues. The experimental results show that the proposed ULCA can completely satisfy the specifications of IBS and stably provide the current gain of 19.9 dB, 3-dB bandwidth of 15 kHz, and input range of -0.4 to 0.4 mA, with only 1.5 nA of dc quiescent current. The input-referred offset and the noise current are 96.6 pA and 37.6 pArms, respectively.