A CMOS fingerprint sensor based on skin resistivity

A novel fingerprint integrated sensor using skin resistivity variation resulting from ridges and valleys on the fingertip is presented. This straightforward detection principle leads to a simpler reading circuitry compared to other integrated fingerprint sensors. The skin resistivity pattern is detected by sweeping the fingertip over a line of 256 pixels. The analog circuits include the pixel input protection against electrostatic discharge, a variable current source, an automatic gain control, and a 1-bit analog to digital converter. The sensor circuit blocks were designed and simulated in a CMOS 0.35 μm process.