Preamplifier Feedback Control for Fast, Low-Oscillation Reset
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Solution Overview
Problem
Existing preamplifier circuits for radiation detectors face challenges in achieving short reset periods and prompt resumption of normal operation after reset, leading to oscillations and increased noise due to high loop gain and leakage currents.
Innovation Solution
A preamplifier circuit design incorporating a feedback circuit with an adjustable transfer function and a loop controller that selectively adjusts the gain and bias of the reset switch, allowing for distinct operating modes to minimize leakage current and reduce oscillations during reset periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reset switch is closed to discharge the feedback capacitor, then the preamplifier circuit can be reset, but oscillations occur due to high loop gain
Solution Approach 1:
The patent changes the loop gain parameter during reset operation by activating a parallel feedback path with controlled gain. This allows the system to maintain stability during reset by adjusting the feedback characteristics, preventing oscillations while still enabling effective capacitor discharge.
Solution Approach 2:
The patent introduces an intermediary feedback path that mediates between the reset switch and the main amplification path. This intermediate path provides controlled feedback during reset operations, preventing the high loop gain from causing oscillations while still allowing the reset function to operate effectively.
2Reliability
If the reset period is extended to ensure complete discharge, then leakage current effects are reduced, but detection performance is degraded due to longer dead time
Solution Approach 1:
The patent implements dynamic control of the feedback path during reset operations, adjusting the feedback characteristics in real-time based on the discharge progress. This dynamic adjustment allows for faster reset times while maintaining adequate leakage current control, as the system adapts its feedback strength throughout the reset period.
Solution Approach 2:
The patent changes feedback parameters during the reset process to optimize both discharge speed and leakage control. By adjusting the feedback gain and characteristics dynamically, the system achieves complete capacitor discharge in shorter time without compromising leakage current management.
3Measurement precision
If the loop gain is increased to improve signal amplification, then detection sensitivity is enhanced, but noise and oscillations increase during reset periods
Solution Approach 1:
The patent segments the feedback function into multiple paths: one for normal operation with high gain for signal amplification, and another for reset operations with controlled gain for stability. This segmentation allows the system to achieve both high signal amplification during detection and low noise during reset by activating the appropriate feedback path.
Solution Approach 2:
The patent implements dynamic switching between different feedback configurations based on operational mode. During normal detection, high loop gain is maintained for sensitivity, while during reset operations, the feedback characteristics are dynamically adjusted to minimize noise and prevent oscillations, achieving both goals at different times.
Data Source
Figure 1~2A
Figure 2B
Figure 2C~3A
AI summary
In accordance with an example embodiment, a preamplifier circuit is provided, the preamplifier circuit comprising an amplifier arranged in a first current path between an input node and an output node of the preamplifier circuit; a feedback capacitor arranged in a second current path between said input node and said output node; a feedback circuit having an adjustable transfer function arranged in a third current path between said input node and said output node; a reset switch arranged in said third current path to enable selectively coupling the output of the feedback circuit to the input of the amplifier and decoupling the output of the feedback circuit from the input of the amplifier; and a loop controller arranged to selectively, in dependence of a voltage in the preamplifier circuit, one of open the reset switch to set the preamplifier circuit in a normal operating mode and close the reset switch to set the preamplifier circuit in a reset mode, wherein the loop controller is arranged to adjust the transfer function of the feedback circuit at least in part in dependence of the current operating mode of the preamplifier circuit.