Integrated Optical Biosensor Pixel with Charge Injection Circuit
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Solution Overview
Problem
Current biosensors, particularly optical biosensors, face challenges in reducing bulkiness and complexity when built using Complementary Metal-Oxide Semiconductor (CMOS) processes, and there is a lack of effective biosensor array architectures that overcome these limitations.
Innovation Solution
The development of an optical biosensor pixel and array architecture that includes an integrated photodiode, optical filter, trans-impedance amplifier, quantizer circuit, charge injection circuit, and feedback network, which convert photon flux into digital signals, and utilize row and column deciders for pixel selection, enabling efficient signal processing and minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical biosensors are built using traditional non-CMOS processes, then detection performance can be achieved, but device complexity and bulkiness increase
Solution Approach 1:
The patent combines multiple previously separate components (photodetector, optical filter, trans-impedance amplifier, quantizer circuit, charge injection circuit, and feedback network) into a single integrated pixel structure fabricated using CMOS processes. This merging of components into one unified device reduces overall system complexity and bulkiness while maintaining detection performance through on-chip integration of all necessary functional elements.
Solution Approach 2:
The CMOS-integrated pixel design serves multiple functions simultaneously: the photodetector converts photons to current, the optical filter selects wavelengths, the trans-impedance amplifier converts current to voltage, the quantizer circuit digitizes the signal, and the charge injection circuit performs background subtraction. This multi-functional integration within a single CMOS device eliminates the need for separate external components, thereby reducing device complexity and bulkiness.
2Ease of manufacture
If signal processing is performed externally, then circuit design is simplified, but signal processing efficiency and integration are reduced
Solution Approach 1:
The patent merges signal processing functions (trans-impedance amplification, quantization, and background subtraction via charge injection) directly into the pixel circuit, eliminating the need for external signal processing components. This integration improves signal processing efficiency by reducing signal path length and minimizing external interference, while the modular pixel design maintains ease of manufacture through standardized CMOS fabrication processes.
3Device complexity
If background subtraction is not performed, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a feedback network that uses a charge injection circuit to perform background subtraction. The feedback mechanism measures the background signal level and injects an equal and opposite charge to cancel out background contributions, thereby improving measurement precision. This feedback-based background subtraction is integrated into the pixel circuit, so it does not significantly increase overall device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in high-performance, compact, and versatile biosensor arrays capable of parallel detection of multiple analytes, reducing bulkiness and complexity while enhancing signal processing and minimizing interference, as demonstrated in applications like bioluminescence-based DNA sequencing.
Implementation Method 1
an integrated photodiode configured to convert an incident photon flux into a current
Implementation Method 2
an integrated optical filter coupled to the integrated photodiode, where the integrated optical filter is configured to select specific wavelengths and/or photon flux angles to reach the integrated photodiode
Data Source
AI summary
An optical biosensor pixel for detecting the amount of light that is generated by the biosensing process and a biosensor array architecture that includes such biosensor pixels. The optical biosensor pixel includes a photodiode configured to convert an incident photon flux into a current. Additionally, the optical biosensor pixel includes an optical filter configured to select specific wavelengths and/or photon flux angles to reach the photodiode from a biological sample. The biosensor pixel further includes a trans-impedance amplifier coupled to the photodiode, where the trans-impedance amplifier is configured to convert the current into a voltage signal. Additionally, the biosensor pixel includes a 1-bit comparator coupled to the trans-impedance amplifier and a 1-bit digital-to-analog converter coupled to the 1-bit comparator, where the 1-bit digital-to-analog converter injects different levels of charge into an input of the trans-impedance amplifier at each cycle based on an output of the 1-bit comparator.