Low Impedance Amplifier for SiPM Timing Readout
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Solution Overview
Problem
The challenge is to simplify the readout architecture for silicon photomultiplier (SiPM) devices in positron emission tomography (PET) systems while maintaining signal integrity, as conventional SiPMs require multiple devices to cover larger areas, leading to increased electronics and power consumption.
Innovation Solution
A multichannel application-specific integrated circuit (ASIC) is developed to interface with arrays of SiPMs, featuring a front-end circuit, a time discriminating circuit with a low input impedance amplifier, and an energy circuit to generate summed signals for timing, energy, and positional information, reducing the impact of combined capacitance and minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple SiPMs are used to cover larger areas, then detection area is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent combines signals from multiple SiPMs using a summing amplifier to create a single timing signal, merging multiple detection channels into one unified readout path. This reduces the number of separate electronics channels needed while maintaining the ability to detect across a larger area covered by multiple SiPM devices.
Solution Approach 2:
The readout electronics is designed to handle both timing-critical signals and energy/position information through a unified architecture. The same summing amplifier and low-input-impedance buffer serve multiple functions: timing discrimination, signal amplification, and capacitance management, eliminating the need for separate dedicated circuits for each function.
2Area of stationary object
If multiple SiPMs are used to cover larger areas, then detection area is improved, but power consumption increases
Solution Approach 1:
By combining signals from multiple SiPMs into a single timing channel using a summing amplifier, the patent reduces the total number of active electronics channels required. Fewer separate amplifiers and processing channels mean lower overall power consumption while still covering a larger detection area through the array of SiPMs.
3Area of stationary object
If conventional readout architecture is used with multiple SiPMs, then detection area is improved, but signal integrity deteriorates due to combined capacitance
Solution Approach 1:
The patent changes the input impedance parameter of the buffer amplifier to a very low value (1 Ohm or less). This parameter change fundamentally alters how the combined capacitance of multiple SiPMs affects the timing signal. The low input impedance creates a dominant time constant that prevents capacitance buildup from degrading signal integrity, even when many SiPMs are connected in parallel.
Solution Approach 2:
The patent converts the harmful effect of combined capacitance from multiple SiPMs into a beneficial feature. By using a low-input-impedance buffer, the combined capacitance of many SiPMs actually helps to filter noise and stabilize the timing signal, transforming what was previously a signal-degrading factor into a signal-improving element.
4Area of stationary object
If multiple SiPMs are used to cover larger areas, then detection area is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple SiPM signal channels into a single timing readout path, reducing the total number of electronics components required. This consolidation lowers manufacturing costs by reducing the number of amplifiers, cables, and processing channels needed, while still achieving large-area coverage through the SiPM array configuration.
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 allows for better timing performance and reduced power consumption, enabling larger arrays of SiPMs with fewer electronics, thus lowering costs and maintaining signal integrity, while reducing the need for individual voltage control and minimizing thermal cooling requirements.
Implementation Method 1
a time discriminating circuit including a low input impedance amplifier configured to be coupled to the array of photodetectors and to receive a signal summing the analog signals from the array of photodetectors and to generate a hit signal for timing pickoff based on the signal
Implementation Method 2
A silicon photomultiplier (SiPM) is an array of passively quenched Geiger-mode avalanche photodiodes (APD) for detecting impinging photons
Implementation Method 3
A silicon photomultiplier (SiPM) is an array of passively quenched Geiger-mode avalanche photodiodes (APD) for detecting impinging photons
Data Source
AI summary
A multichannel ASIC for interfacing with an array of photodetectors in a PET imaging system includes a front-end circuit configured to be coupled to the array of photodetectors and to receive analog signals therefrom. The ASIC includes a time discriminating circuit including a low input impedance amplifier configured to be coupled to the array of photodetectors and to receive a signal summing the analog signals from the array of photodetectors and to generate a hit signal for timing pickoff based on the signal. The ASIC includes an energy circuit operably coupled to the front-end circuit and configured to generate a summed energy output signal based on each of the analog signals and summed positional output signal based on each of the analog signals.