Design of Picoammeter for Test and Measurement

Semiconductor testing frequently involves low current measurement. Some of the tests may include leakage current testing, low current measurements related to dielectric for wafer level semiconductors. These low current measurements can be made using picoammeter. This study aims to create a picoammeter circuit design to measure pico ampere value using instrumentation amplifier as opposed to operational amplifier for test and measurement. To ensure that this design provides acceptable results, simulations to test accuracy, noise, and settling time were performed using low noise and low input bias current instrumentation amplifiers for picoammeter circuits. The test shows that all selected instrumentation amplifiers used yield accurate results. AD8421 performs best for a low noise picoammeter whereas, AD8422 performs best for a fast-settling picoammeter. AD8224, AD8220, and AD8422 performs best when considering both parameters that still gives accurate results.