In-Pixel Passive Amplification for CMOS Image Sensors
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Solution Overview
Problem
Traditional CMOS image sensors face challenges with signal-to-noise performance due to the need for storage capacitors, which introduce noise, and existing in-pixel amplification methods require multiple components, reducing quantum efficiency.
Innovation Solution
In-pixel passive amplification using a voltage-controlled capacitor with variable capacitance, eliminating the need for storage capacitors and PMOS devices, allowing for fewer components and higher quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If traditional storage capacitors are used to store pixel outputs, then temporary storage is achieved, but thermal noise increases due to limited capacitance
Solution Approach 1:
The patent applies preliminary action by performing signal amplification immediately after photoelectric conversion within the same pixel, before the signal is transferred to storage capacitors. This in-pixel amplification ensures that the signal is strengthened before storage, eliminating the need for large storage capacitors and thereby reducing thermal noise while maintaining temporary storage capability.
2Power
If PMOS devices are used in existing in-pixel amplification methods, then amplification gain is achieved, but quantum efficiency decreases
Solution Approach 1:
The patent applies parameter changes by transitioning from active amplification using PMOS devices to passive amplification using capacitance modulation. By changing the amplification mechanism from transistor-based active devices to capacitor-based passive devices, the patent eliminates the quantum efficiency penalty associated with PMOS devices while maintaining amplification gain through variable capacitance control.
3Power
If multiple components are used for in-pixel amplification, then amplification function is achieved, but device complexity and area increase
Solution Approach 1:
The patent applies merging by integrating the amplification function directly into the pixel structure using shared capacitors and control circuits. The variable capacitance amplifier uses capacitors that can be controlled by external signals, allowing amplification functionality to be combined with existing pixel components rather than requiring separate dedicated amplification components for each pixel.
4Power
If active amplification devices are used, then amplification gain is achieved, but power consumption increases
Solution Approach 1:
The patent applies mechanics substitution by replacing active electronic amplification devices (which consume power through transistor operation) with a passive capacitive amplification system. The amplification is achieved through mechanical-like capacitance modulation controlled by external voltage signals, eliminating the continuous power consumption associated with active devices while maintaining amplification gain.
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 reduces noise and power consumption, enabling faster operation and higher quantum efficiency while maintaining a small footprint, as it uses NMOS transistors and consumes less power compared to active devices.
Implementation Method 1
The passive amplifier includes a voltage-controlled capacitor adapted to receive and store the input voltage signal at a first terminal. The capacitance of the voltage-controlled capacitor is variable between a first and second capacitance in response to a capacitor control voltage. Varying the voltage-controlled capacitor from a first capacitance to a second capacitance subjects the input voltage signal stored at the first terminal to a gain, thereby generating an output voltage signal at the first terminal.
Data Source
AI summary
A pixel for converting incident subatomic particles into an output voltage signal is disclosed. In one aspect, the pixel includes a photo-detector adapted to receive incident subatomic particles and generate an input voltage signal corresponding to an intensity of the received particles. The pixel also includes a passive amplifier adapted to passively amplify the input voltage signal to generate an output voltage signal. The passive amplification reduces the noise of the output voltage signal, and may have a higher quantum efficiency than typical in-pixel amplification devices and methods.