Patent ID: 11886666
Assignee: HIMAX TECHNOLOGIES LIMITED
Field: Basic communication processes (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 7:
8. A fingerprint detection system, comprising:
a sensor panel including:
a photo diode having an anode electrode connected to a first common-mode voltage and a cathode electrode providing a photo-detected voltage; and
a sampling switch coupled to receive the photo-detected voltage;

a detection circuit including:
an integrator coupled to receive the photo-detected voltage via the sampling switch and configured to generate time integral of the photo-detected voltage, thereby resulting in a time-integral signal; and
an analog-to-digital converter (ADC) that converts the time-integral signal into a digital form;

wherein the first common-mode voltage is coupled to the integrator to prevent noise occurred in the first common-mode voltage from affecting the time-integral signal;
wherein the integrator comprises:
an integrating amplifier; and
an integrating capacitor connected between an output node and an inverting input node of the integrating amplifier;

wherein the detection circuit comprises:
a conversion switch connected between the integrator and the ADC; and
a conversion capacitor connected between an input node of the ADC and ground;, wherein the detection circuit comprises:
a first buffer amplifier;
a second buffer amplifier that provides a first reference voltage; and
a first voltage adder that adds the first common-mode voltage and the first reference voltage, thereby resulting a sum voltage fed to a non-inverting input node of the first buffer amplifier, which provides the first reference voltage to a non-inverting input node of the integrating amplifier.