Charge Preamplifier Feedback Reset With High-Frequency Noise Attenuation
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Solution Overview
Problem
Charge preamplifiers for charge source sensors face noise issues due to active reset systems, which introduce fluctuations in signal measurement, especially when the discharging current increases during signal detection, making it difficult to maintain low noise levels both in static and dynamic operations.
Innovation Solution
A charge preamplifier with a control element that generates a control signal proportional to the deviation between the output voltage and a reference voltage, with a proportionality coefficient lower than one in high frequency bands, to regulate the reset system and reduce noise by attenuating the discharging current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an active reset system (SRZ component) is used to discharge the storage capacitor, then the reset function is achieved and the operational amplifier saturation is avoided, but the active element introduces noise that increases with the discharging current, especially during dynamic operation when a signal is present
Solution Approach 1:
A control element is introduced as an intermediary between the output of the phase inverting amplifier and the reset system. This control element generates a control signal that is proportional to the deviation between the output voltage and reference voltage, but with a proportionality coefficient lower than one in high frequency bands. This intermediary attenuates the control signal at high frequencies, thereby reducing the discharging current and the associated noise during dynamic operation, while still allowing the reset system to function effectively.
2Speed
If the proportionality coefficient of the control element is high, then the voltage regulation is more aggressive and the reset is faster, but the discharging current increases and generates more noise during signal detection
Solution Approach 1:
The control element is designed with frequency-dependent characteristics, where the proportionality coefficient varies with frequency. At low frequencies (static operation), the coefficient allows for adequate voltage regulation. At high frequencies (dynamic operation during signal detection), the coefficient is reduced to attenuate the control signal, thereby reducing the discharging current and noise. This dynamic adjustment of the control parameter resolves the contradiction between reset speed and noise generation.
3Object-generated harmful factors
If a high resistance value is used in the reset system, then the noise from the resistance is reduced, but the discharging capability is insufficient and the operational amplifier may saturate
Solution Approach 1:
The patent replaces the passive resistance-based reset system with an active reset system using an SRZ (voltage-controlled current source) component. This active component can provide sufficient discharging current to prevent operational amplifier saturation while introducing controllable noise. The noise issue is then addressed by introducing the control element with frequency-dependent attenuation, which reduces the discharging current and associated noise during high-frequency dynamic operation while maintaining the discharging capability during static or low-frequency conditions.
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 effectively restricts noise by controlling the discharging current and maintaining accurate voltage regulation, reducing signal fluctuations and improving measurement precision by acting as an attenuator in high frequency bands and amplifier in low frequency bands.
Implementation Method 1
a control element connected between the reset system and the output of the phase inverting amplifier, and suitable for providing the control signal to the reset system, said control signal being proportional to the deviation between the output voltage of the phase inverting amplifier and a reference voltage, said proportionality coefficient being lower that one for high frequencies
Implementation Method 2
the 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
Implementation Method 3
a storage capacitor Cm, called a 'storage capacitor ', collecting the charge delivered by the sensor CAP
Implementation Method 4
a phase inverting amplifier AI, herein of the operational type, and a capacitor Cm, called a 'storage capacitor ', collecting the charge delivered by the sensor CAP
Data Source
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.