In applications that require low leakage current, it’s important to select a low-input-bias-current (IB) operational amplifier. The application note AN-1373 describes how to measure ultra-low bias current using the ADA4530-1 evaluation board. However, due to the nature of handling femtoampere-level currents, the measurement environment—equipment such as jigs, shields, cables, and connectors—also affect the measurement results.
This article will introduce a trial to recreate the measurement in AN-1373 using commonly available commercial-grade lab equipment, jigs, and materials, and includes some workarounds to improve the measurement to finally achieve 50 fA.