Pixel Differential Amplifier Circuit for Floating Diffusion Dynamic Range
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Solution Overview
Problem
The existing imaging apparatus configuration results in a reduction of the dynamic range of the floating diffusion layer due to voltage drops in the differential amplifier circuit, which affects the reset potential and image quality.
Innovation Solution
The proposed imaging apparatus includes a configuration with a clamp capacitance connected in series between the floating diffusion layer and the amplifier transistor, and a reset transistor connected in parallel between the floating diffusion layer and the clamp capacitance, preventing voltage drops from influencing the reset potential and maintaining the dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a differential amplifier circuit is used to amplify the voltage signal from the floating diffusion layer, then the signal amplification is improved, but the dynamic range of the floating diffusion layer is reduced due to voltage drops in the amplifier transistor
Solution Approach 1:
The patent divides the pixel structure into separate functional regions: the floating diffusion layer is physically and electrically separated from the differential amplifier circuit. This segmentation allows the floating diffusion layer to maintain its full dynamic range while the amplifier circuit performs its amplification function independently, eliminating the voltage drop issue that occurs when they are directly connected.
Solution Approach 2:
The patent introduces an intermediary mechanism (separate node structure) between the floating diffusion layer and the differential amplifier input. This intermediary allows the amplifier to receive the voltage signal without directly affecting the floating diffusion layer's potential, thus preventing the voltage drop from propagating back to the floating diffusion layer and preserving its dynamic range.
2Reliability
If the floating diffusion layer is reset during Auto-zero operation of the differential amplifier, then the amplifier initialization is improved, but the reset potential is reduced due to voltage drops
Solution Approach 1:
The patent segments the reset operation from the amplifier circuit by providing a dedicated reset path for the floating diffusion layer that is independent of the amplifier's Auto-zero operation. This allows the floating diffusion layer to be reset to its proper potential without being affected by the voltage drops that occur in the amplifier transistor during initialization.
3Measurement precision
If an AD converter is provided for each pixel to convert the voltage signal, then the conversion precision is improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple AD converters into a shared resource that serves multiple pixels. Instead of providing a dedicated AD converter for each pixel, the design allows multiple pixels to share common amplification and conversion resources, thereby reducing the overall device complexity while maintaining the precision benefits of per-pixel conversion capability when needed.
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 prevents the reduction in dynamic range of the floating diffusion layer, ensuring improved image quality by isolating the reset potential from voltage drops in the differential amplifier circuit.
Implementation Method 1
a conversion element converting incident light into photoelectrons
Implementation Method 2
a floating diffusion layer electrically connected to the conversion element and converting the photoelectrons into a voltage signal
Data Source
AI summary
Provided is an imaging apparatus including an imaging unit having a plurality of pixels, the pixels each having: a conversion element converting incident light into photoelectrons; a floating diffusion layer electrically connected to the conversion element and converting the photoelectrons into a voltage signal; a differential amplifier circuit electrically connected to the floating diffusion layer, including an amplifier transistor to which a potential of the floating diffusion layer is input, and amplifying the potential of the floating diffusion layer; a feedback transistor electrically connected to the amplifier transistor and initializing the differential amplifier circuit; a clamp capacitance connected in series between the floating diffusion layer and the amplifier transistor; and a reset transistor connected in parallel between the floating diffusion layer and the clamp capacitance and initializing the potential of the floating diffusion layer.