Photon Counting OTA Tuning for Uniform Gain and Peaking Time
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Solution Overview
Problem
Photon counting systems face challenges with high power consumption, image artifacts due to varying input capacitances, and inefficient cooling requirements, especially in large systems with non-integrated sensors and frontend circuits, leading to performance disparities across channels.
Innovation Solution
A circuit arrangement with tunable operational transconductance amplifiers (OTAs) and feedback networks that equalize bandwidth and noise levels across stages by adjusting transconductance based on input capacitance, using noise injection blocks and heaters to balance performance and minimize power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of channels for photon counting is increased to achieve high spatial resolution, then spatial resolution is improved, but power consumption increases requiring expensive cooling
Solution Approach 1:
The sensor and frontend circuit are merged into a single integrated device, eliminating the need for external connections and reducing parasitic capacitances. This integration allows for efficient photon counting with reduced power consumption per channel, enabling high spatial resolution systems without proportionally increasing cooling requirements
Solution Approach 2:
The input capacitance is adjusted by modifying the physical structure of the frontend circuit (reducing connection lengths and parasitic elements). By changing the capacitance parameter to lower values through integration, the power consumption and cooling requirements are reduced while maintaining high spatial resolution capability
2Adaptability or versatility
If the sensor and frontend circuit are connected externally, then flexibility in circuit design is improved, but parasitic input capacitances increase affecting noise behavior and speed
Solution Approach 1:
The sensor and frontend circuit are combined into a single integrated device where the frontend circuit is fabricated directly on the sensor substrate. This eliminates external connections and associated parasitic capacitances, while the circuit design remains flexible through standard semiconductor fabrication processes that allow various circuit configurations
3Ease of operation
If connection lengths between sensor and frontend circuit vary across channels, then routing flexibility is improved, but input capacitances become non-uniform causing image artifacts
Solution Approach 1:
By integrating the frontend circuit directly on the sensor, all channels benefit from uniformly short and controlled connection lengths. This eliminates the variability in input capacitances that would otherwise require complex routing adjustments, while maintaining full routing flexibility through on-chip circuit design
Solution Approach 2:
The integrated structure ensures that all channels have identical or closely matched input capacitances due to uniform fabrication processes. This homogeneity in electrical characteristics across channels eliminates image artifacts while preserving routing flexibility through standardized circuit layouts
4Manufacturing precision
If through silicon vias are used to enable direct connection, then input capacitance uniformity is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The sensor and frontend circuit are merged using standard semiconductor integration techniques on a single substrate. This approach achieves uniform input capacitances without requiring complex through-silicon via processes, reducing manufacturing complexity while maintaining capacitance uniformity across all channels
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
The solution enables efficient operation with uniform performance parameters, reduced power consumption, and cost-effective cooling, thereby preventing image artifacts and enhancing imaging device efficiency.
Implementation Method 1
Each stage comprises a tunable operational transconductance amplifier (OTA) comprising an amplifier input and an output. That the OTA is tunable can mean, that the transconductance of the OTA can be tuned or adjusted
Implementation Method 2
Each stage further comprises a feedback network that is connected to the amplifier input and to the output of the OTA thereby forming a feedback loop of the OTA
Implementation Method 3
for each stage a noise injection block is connected to a further input of the OTA. This noise injection block is configured to inject noise to the respective OTA
Implementation Method 4
each heater is configured to heat its environment
Data Source
AI summary
A circuit arrangement is provided which includes an array of stages for photon counting current to voltage conversion. Each stage includes a tunable operational transconductance amplifier and a feedback network forming a feedback loop of the operational transconductance amplifier. Each stage is configured to provide an output signal as a function of an input signal that is provided to the amplifier input of the operational transconductance amplifier, wherein the input signal comprises one or more current pulses and the output signal comprises one or more voltage pulses. With the tunable operational transconductance amplifier the transconductance of a stage can be tuned so that differences in peaking time and gain are avoided. Furthermore, an imaging device and a method for operating a circuit arrangement are provided.