Differential Amplifying Circuit Layout for Low-Noise Image Sensor Output
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Solution Overview
Problem
Image sensors in camera devices face challenges in achieving high-quality image data due to noise generated by transistors operating at various voltages, which affects the accuracy of light intensity detection and signal processing.
Innovation Solution
An electronic circuit design that includes a load circuit, an input circuit, and a current generating circuit, utilizing transistors to generate and manage currents based on operating voltages, allowing for the output of a voltage that amplifies the difference between input voltages, thereby reducing noise and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transistors operate at various operating voltages to process signals from pixels, then signal processing capability is improved, but noise is generated affecting image quality
Solution Approach 1:
The circuit is divided into multiple differential stages (first differential circuit, second differential circuit) with separate current paths. Each stage processes signals independently using segmented current sources (first current, second current, third current, fourth current), allowing noise from individual transistors to be isolated and not propagated throughout the entire circuit.
Solution Approach 2:
The patent converts the harmful noise effect by using differential signaling throughout the circuit. The differential configuration (comparing first input voltage with second input voltage, then third input voltage with fourth input voltage) inherently rejects common-mode noise. Additionally, the circuit uses current mirrors and differential pairs to convert voltage noise into controlled current differences, transforming random noise into predictable signal differences that can be amplified cleanly.
2Adaptability or versatility
If multiple transistors are used to process signals at different voltages, then functionality is improved, but noise affecting light intensity detection accuracy increases
Solution Approach 1:
The circuit employs feedback through current mirrors and differential configurations. The current generating circuit uses feedback loops where the first current mirror circuit mirrors currents from the first differential circuit to the second differential circuit, and the second current mirror circuit mirrors currents from the second differential circuit back. This feedback mechanism stabilizes the operating points and reduces the impact of transistor noise on measurement precision.
Solution Approach 2:
The patent introduces intermediary current sources and current mirrors between the input stage and output stage. The first current generating circuit generates intermediate currents (first current, second current) that serve as mediators, and the second current generating circuit generates additional intermediary currents (third current, fourth current). These intermediary currents buffer and isolate the input signals from the output, preventing noise propagation and maintaining detection accuracy.
3Device complexity
If a simple amplifying circuit is used, then device complexity is reduced, but noise reduction capability is insufficient
Solution Approach 1:
The patent merges multiple functions into a unified differential amplification architecture. The first differential circuit and second differential circuit are merged into a single cascaded structure where the output of the first stage feeds into the second stage. The current generating circuits are merged to provide coordinated current sources for both differential stages. This merging achieves noise reduction through differential signaling while maintaining relatively simple circuit topology.
Data Source
AI summary
An electronic circuit is provided. The electronic circuit includes a first current generating circuit configured to output a first operating current based on a first operating voltage; and an input circuit configured to: receive a first current corresponding to a first input voltage and a second current corresponding to a second input voltage, wherein the first current and the second current are based on the first operating current; receive a third current and a fourth current that are generated based on the first operating voltage; and generate a fifth current corresponding to the second input voltage based on a second operating current. The electronic circuit is configured to generate an output voltage that is associated with a difference between the first input voltage and the second input voltage based on the second current, the fourth current and the fifth current, and the fourth current corresponds to the third current.