Photodiode Bias Feedback Circuit for Low-Noise Image Sensing
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Solution Overview
Problem
Conventional solid-state image sensors face challenges in maintaining a stable excess bias due to variations in breakdown voltage and temperature, leading to decreased sensitivity and increased dark current noise.
Innovation Solution
A solid-state image sensor configuration that includes a photodiode, a resistor connected to its cathode, and a control circuit that adjusts the anode potential based on the cathode potential when a photocurrent flows through the resistor, thereby controlling the excess bias to an appropriate value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the excess bias is increased to improve sensitivity, then the sensitivity of the photodiode is improved, but the dark current noise increases
Solution Approach 1:
The control circuit monitors the cathode potential and dynamically adjusts the anode potential to maintain a stable excess bias value. This feedback mechanism ensures that the excess bias remains within an optimal range, preventing both sensitivity degradation and excessive dark current noise generation.
Solution Approach 2:
The patent dynamically changes the anode potential parameter based on the measured cathode potential to maintain a stable excess bias. By adjusting the anode potential in response to cathode potential variations, the system optimizes the balance between sensitivity and dark current noise.
2Stability of the object's composition
If manual adjustment is performed for each product to suppress excess bias fluctuation, then the stability of excess bias is improved, but the labor and time required increases
Solution Approach 1:
The control circuit automatically measures the cathode potential and adjusts the anode potential accordingly, eliminating the need for manual adjustment. This automated feedback system maintains excess bias stability while significantly reducing the time and labor required compared to manual adjustment for each product.
Solution Approach 2:
The system performs self-adjustment by automatically monitoring its own cathode potential and correcting the anode potential to maintain optimal excess bias. This self-service capability eliminates the need for external manual intervention during product setup.
3Stability of the object's composition
If the excess bias becomes too small to suppress fluctuation, then the stability is improved, but the sensitivity of the photodiode decreases
Solution Approach 1:
The control circuit continuously monitors the cathode potential and adjusts the anode potential to maintain the excess bias within an optimal range. This feedback ensures that the excess bias remains stable without becoming too small, thereby preserving photodiode sensitivity while achieving fluctuation suppression.
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 configuration effectively suppresses fluctuations in the anode potential, enhancing the sensitivity of the photodiode while reducing dark current noise and labor-intensive adjustments.
Implementation Method 1
a photodiode configured to photoelectrically convert incident light and output a photocurrent
Implementation Method 2
a resistor connected to a cathode of the photodiode... when the photocurrent flows through the resistor
Data Source
AI summary
To control an excess bias to an appropriate value in a light detection device.A solid-state image sensor includes a photodiode, a resistor, and a control circuit. In this solid-state image sensor, the photodiode photoelectrically converts incident light and outputs a photocurrent. Furthermore, in the solid-state image sensor, the resistor is connected to a cathode of the photodiode. Furthermore, in the solid-state image sensor, the control circuit supplies a lower potential to an anode of the photodiode as a potential of the cathode of when the photocurrent flows through the resistor is higher.