Charge Preamplifier Reset Control for Low-Noise Measurement
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Solution Overview
Problem
Charge preamplifiers for charge source sensors face noise issues due to the active reset system, which increases noise variance when measuring signals, as the discharge current changes from a low quiescent value to a higher value upon signal arrival, affecting measurement accuracy.
Innovation Solution
A charge preamplifier with a control element that generates a control signal proportional to the difference between the output voltage and a reference voltage, with a proportionality coefficient less than one in high frequency bands, to attenuate the discharge current and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an active reset system is used to discharge the memory capacitor, then the reset function is achieved, but noise variance increases during signal measurement
Solution Approach 1:
The patent applies dynamics by making the discharge current adjustable rather than fixed. The control element dynamically modulates the discharge current based on the signal amplitude, using a modulation signal that varies the discharge current proportionally to the signal level. This dynamic adjustment allows the system to maintain low noise during small signals while still achieving effective reset during large signals.
Solution Approach 2:
The patent changes the parameter of discharge current from a constant value to a variable value that depends on the signal amplitude. By introducing a modulation signal that controls the discharge current proportionally, the system transforms the fixed parameter into a dynamic one, thereby reducing noise variance during measurement while maintaining reset functionality.
2Reliability
If the discharge current is increased to ensure adequate resetting, then the reset effectiveness is improved, but noise fluctuations increase during measurement
Solution Approach 1:
The patent changes the discharge current from a fixed high value to a variable value that scales with the signal amplitude. The modulation signal ensures that the discharge current is proportional to the signal level, thereby maintaining reset effectiveness when needed while minimizing noise fluctuations during measurement of smaller signals.
Solution Approach 2:
The system uses feedback by deriving the modulation signal from the output voltage of the phase-inverting amplifier. This feedback mechanism ensures that the discharge current is automatically adjusted according to the actual signal level, creating a self-regulating system that balances reset effectiveness with noise reduction.
3Measurement precision
If a high resistance value is used for permanent reset, then noise from the resistor is reduced, but the discharge capability is insufficient
Solution Approach 1:
The patent introduces a control element as an intermediary between the memory capacitor and the discharge path. This control element modulates the discharge current based on the signal amplitude, acting as a mediator that allows the system to achieve both low noise (by avoiding high fixed resistance) and sufficient discharge capability (by actively controlling the current when needed).
Solution Approach 2:
The patent replaces the passive mechanical resistor-based reset system with an active electronic control system. Instead of relying on a fixed high-value resistor, the system uses an electronically controlled discharge mechanism that can dynamically adjust the discharge current, thereby achieving both low noise and adequate discharge capability.
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 solution limits noise fluctuations during signal measurement by controlling the discharge current, maintaining low noise levels even when measuring signals, thereby improving measurement accuracy.
Implementation Method 1
The control element (241) is connected between the reset system (242) and the output (204) of the phase-inverting amplifier (201), and is adapted to supply the control signal to the reset system (242), said control signal being proportional to the difference between the output voltage of the phase-inverting amplifier (201) and a reference voltage
Implementation Method 2
a memory capacitor (202) connected between the input (203) and an output (204) of the phase-inverting amplifier (201)
Implementation Method 3
a phase inverting amplifier (201) comprising an input (203) linked to the charge source sensor (205), an output (204)
Implementation Method 4
a reset system (242) connected to the input (203) of the inverting amplifier phase, to supply the memory capacitor (202) with a discharge current according to a control signal
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
A charge preamplifier for converting an electric charge generated in a charge source sensor into a voltage signal, including: a phase inverting amplifier including an input related to the charge source sensor, and an output for providing the voltage signal; a storage capacitor connected between the input and the output of the phase inverting amplifier; a reset system connected to the input of the phase inverting amplifier, for providing to the storage capacitor a discharging current as a function of a control signal, and a control element including: a first input connected to the output of the phase inverting amplifier, for withdrawing the voltage signal, a second input subjected to a reference voltage, a set of components configured and arranged to generate a control signal proportional to the deviation between the voltage signal and the reference voltage, the proportionality coefficient being lower than one in a high frequency band, an output connected to the reset system to provide thereto the control signal.