Dual-Switch Charge Amplifier for Low-Noise Wide Charge Range
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Solution Overview
Problem
Existing charge sensitive amplifier circuits for sensor frontends face challenges in optimizing noise without limiting the charge input range, particularly in line sensors with high dynamic input charge ranges.
Innovation Solution
The proposed charge sensitive amplifier circuit employs a dual transfer switch configuration, where a first transfer switch is controlled to maintain high conductivity at the beginning of charge transfer and reduce conductivity at the end, while a second transfer switch is used in parallel to assist in transferring large charges without compromising noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transistor switch is used to transfer charge, then the device complexity is reduced, but the bandwidth is insufficient to remove all charges during the transfer phase while meeting low noise requirements
Solution Approach 1:
The charge transfer function is segmented into two parallel paths: a first transfer switch for normal operation and a second transfer switch for high-charge conditions. This segmentation allows the system to handle different charge levels with appropriate bandwidth, removing the limitation of a single switch while avoiding the complexity of a continuously adjustable system.
2Measurement precision
If the bandwidth of the charge sensitive amplifier is increased to improve settling accuracy during short transfer times, then the transfer speed is improved, but the noise of the input stage increases
Solution Approach 1:
The system dynamically adjusts the effective bandwidth by selectively activating the second transfer switch based on charge magnitude. For small charges, only the first switch operates with lower bandwidth, minimizing noise. For large charges, both switches operate in parallel to provide higher bandwidth and faster transfer, thus dynamically adapting to different operating conditions.
Solution Approach 2:
The bandwidth parameter is changed based on the charge magnitude. By detecting the charge level and activating appropriate transfer switches, the system changes the effective bandwidth from low (first switch only) to high (both switches parallel), optimizing both noise performance and transfer speed for different charge conditions.
3Object-affected harmful factors
If the bandwidth is reduced at the end of charge transfer to optimize noise, then the noise performance is improved, but the charge transfer time increases
Solution Approach 1:
The second transfer switch is preliminarily positioned in parallel with the first switch, ready to be activated when large charges are detected. This preliminary configuration allows the system to immediately engage high-bandwidth transfer when needed, avoiding the time penalty of gradually increasing bandwidth during the transfer process.
4Adaptability or versatility
If a high dynamic range is required to handle varying input charges, then the adaptability is improved, but the bandwidth requirements increase beyond what a single switch can provide
Solution Approach 1:
The first transfer switch serves multiple functions: it handles normal charge transfer operations and works in conjunction with the second switch for high-charge conditions. The second switch specifically handles excessive charge removal. This multi-functionality allows a single switch configuration to adapt to a wide dynamic range of input charges without requiring excessively high bandwidth for all conditions.
Data Source
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AI summary
A charge sensitive amplifier circuit (1) for sensor frontend comprises an input node (I) to be connected to a sensor (2) to receive an input charge, and an output node (O) to be connected to a charge conversion circuit (3). The charge sensitive amplifier circuit (1) comprises a first transfer switch (10) located between the input node (I) and the output node (O) to transfer the input charge to the output node (O). The charge sensitive amplifier circuit (1) further comprises a second transfer switch (20) located in parallel to the first transfer switch (10) between the input node (I) and the output node (O) to transfer the input charge to the output node (O).