Performance comparison of low current measurement systems for biomedical applications

In this paper, we report on the noise analysis of low current measurement systems for biomedical applications. We analyzed resistive feedback, capacitive feedback and current conveyor circuits for low current measurement systems. Detailed noise analysis are presented and matched with measurement data using a 0.5-μm fabrication process. Based on the theoretical analysis and the measurements, the capacitive feedback system provides better noise performance for the measurement of low current. The capacitive feedback is capable of measuring 700fA RMS at 10KHz sampling rate, whereas the resistive feedback provides 4pA and the current conveyor provides 600pA. This paper provides design guidelines to maximize the measurement performance of low current for biomedical instrumentation.