Signal Processing Apparatus Suppressing RTS Noise in Image Sensors
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Solution Overview
Problem
Existing methods fail to effectively suppress random telegraph signal (RTS) noise in transistors, leading to decreased image quality in image sensors due to increased noise levels and vertical streaks in captured images.
Innovation Solution
A signal processing apparatus with an amplifying transistor and a short-circuit unit that short-circuits the transistor's gate to a potential reducing the gate-to-source voltage, particularly during non-operating states, to mitigate RTS noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the input transistor in a differential stage is increased in size in an A/D converter, then RTS noise is suppressed, but other noise such as kickback noise and simultaneous inversion noise is aggravated
Solution Approach 1:
The patent applies preliminary action by performing auto-zeroing before the actual signal processing. The short-circuit unit short-circuits the gate and drain of the input transistor during a predetermined period (before signal input) to remove offset voltage and reduce RTS noise in advance. This preliminary reset action prevents the transistor from operating in a state that would generate kickback noise and simultaneous inversion noise during subsequent signal processing.
Solution Approach 2:
The patent implements periodic action by alternating between short-circuiting the gate and drain during a predetermined period and then separating them during signal processing periods. This periodic switching between reset state (gate shorted to drain) and operating state allows the system to reduce noise periodically while maintaining normal functionality, thereby suppressing both RTS noise and preventing kickback noise through rhythmic reset cycles.
2Object-affected harmful factors
If noise is injected on purpose to reduce the effect of RTS noise, then RTS noise effect is reduced, but the absolute value of noise is increased
Solution Approach 1:
The patent extracts and removes the noise component through auto-zeroing. By short-circuiting the gate and drain during a reset period, the offset voltage and RTS noise are captured and removed from the signal path. This extraction approach eliminates the need to inject additional noise, as the noise reduction is achieved by removing the problematic voltage offsets that cause RTS noise effects, thereby reducing both RTS noise effect and absolute noise value.
Solution Approach 2:
The patent converts the harmful offset voltage and RTS noise into a beneficial reset state. During the predetermined period, the gate and drain are short-circuited, which causes the noise and offset to manifest as a measurable voltage that can then be eliminated. This converts the harmful noise effect into a useful reset condition, allowing the system to achieve noise reduction without injecting additional noise, thereby resolving the contradiction between reducing RTS noise effect and minimizing absolute noise value.
3Object-affected harmful factors
If a built-in transistor is used to suppress RTS noise, then RTS noise is reduced, but process modification is required and cost increases
Solution Approach 1:
The patent makes the existing input transistor multi-functional by adding the short-circuit unit that can connect the gate and drain. This modified transistor serves both as the signal processing transistor and as an auto-zeroing element. The same transistor structure is used for both normal operation and noise suppression, eliminating the need for separate built-in transistors and avoiding process modifications. This universal approach reduces RTS noise without increasing manufacturing complexity or cost.
Solution Approach 2:
The patent merges the noise suppression function with the existing input transistor circuitry. The short-circuit unit combines the gate and drain of the same transistor during reset periods, integrating the auto-zeroing function into the existing transistor structure. This merging eliminates the need for separate built-in transistors or process modifications, achieving RTS noise suppression using the same transistor that performs signal processing, thereby maintaining ease of manufacture and controlling costs.
Data Source
AI summary
The present technology relates to a signal processing apparatus, a control method, an image pickup element, and an electronic device which make it possible to suppress RTS noise. The signal processing apparatus of the present technology may include an amplifying transistor and a short-circuit unit. The amplifying transistor amplifies a signal input to a gate, and the short-circuit unit is capable of short-circuiting the gate of the amplifying transistor to a potential which reduces a gate-to-source voltage of the amplifying transistor. For example, it is determined whether the amplifying transistor is in a period of a non-operating state, and when the amplifying transistor is determined to be in the period of a non-operating state, the gate of the amplifying transistor may be short-circuited. The present technology can be applied, for example, to an image pickup element and an electronic device.