Low capacitance sensing circuit for fingerprint sensor integrated into display screen based on charging and extracting process

Abstract

In this paper, a sensitive and simple structure to measure low mutual capacitance of fingerprint sensor in 130-nm CMOS technology is presented. The proposed fingerprint sensor is integrated with display screen. Present sensing structures use projective capacitive touch technique. However, the new structure applies charging and extracting process (CEP). As using the CEP, the circuit challenges another different fingerprint sensor combined with display screen. Also, the current difference between ridge and valley is about 25 nA.