Native N-channel MOSFET CIS Sensor RTS Noise Reduction
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Solution Overview
Problem
CMOS image sensors suffer from Random Telegraph Signals (RTS) noise, particularly in low light applications and downscaled transistor dimensions, which affects image quality, and existing methods consume excessive power due to high resolution and high-speed imaging requirements.
Innovation Solution
The image sensing system employs native N-channel MOSFETs to generate biasing current, reducing RTS noise and power consumption by using a smaller circuit size, and incorporates a capacitor dividing circuit to generate a signal with a predetermined threshold for digital output conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional MOSFETs are used in CIS sensors, then the circuit can provide sufficient current driving capability, but RTS noise increases and power consumption rises
Solution Approach 1:
The patent changes the fundamental parameter of the MOSFET by using a native channel device instead of a conventional enhanced-mode MOSFET. This parameter change in the transistor type inherently reduces RTS noise and power consumption while maintaining the required current driving capability for the image sensor circuit
2Measurement precision
If transistor dimensions are downscaled to increase pixel density, then resolution improves, but RTS noise increases significantly
Solution Approach 1:
The patent applies parameter change by switching to native channel MOSFETs, which have different electrical characteristics that are inherently less susceptible to RTS noise even at scaled dimensions. This allows the circuit to maintain high resolution through downscaling while the native device parameter prevents the associated RTS noise increase
3Measurement precision
If high-resolution CIS pixels are implemented, then image quality improves, but the reading circuit occupies larger area and consumes more power
Solution Approach 1:
By changing the MOSFET parameter to native channel type, the circuit achieves higher efficiency in current driving capability. This parameter change allows the reading circuit to maintain high-resolution signal processing with reduced device size and lower power consumption, thus occupying less area
Data Source
AI summary
A sensing device includes: a sampling circuit arranged to sample a sensing signal for generating a signal in response to a sampling signal having a monotonically increasing waveform; and a conversion circuit arranged to convert the signal into a digital output signal when the signal reaches a predetermined threshold of the conversion circuit.