Sample-and-Hold Circuit Charging Path for Low-Distortion Sampling
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Solution Overview
Problem
Sample and hold circuits introduce distortion in sampled signals due to lead inductance, which limits the spurious free dynamic range and is particularly problematic in high-speed and high-resolution Analog to Digital Converter (ADC) applications.
Innovation Solution
The solution involves charging an energy storage element through a path with reduced lead inductance, thereby minimizing the energy drawn through the input path and reducing distortion, and using an additional energy storage device to supply part of the energy during the sampling phase, reducing the total energy drawn through the input path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the energy storage element is charged through the input path, then the signal is sampled, but lead inductance causes distortion and oscillations
Solution Approach 1:
The charging current path is segmented into two separate paths: one path (first path) with reduced lead inductance for charging the energy storage element, and another path (second path) with higher lead inductance that is avoided during charging. This segmentation allows the sampling function to be performed while minimizing the harmful effects of lead inductance on signal integrity.
Solution Approach 2:
An intermediary switching mechanism is introduced to selectively connect the energy storage element to different paths. The switch enables the circuit to choose the low-inductance path for charging operations, thereby mediating between the need to sample the signal and the need to avoid distortion caused by lead inductance.
2Productivity
If high-speed sampling is performed, then productivity increases, but distortion and oscillations worsen
Solution Approach 1:
The circuit employs dynamic switching to adaptively select the charging path based on operational requirements. During high-speed sampling modes, the switch dynamically connects to the low-inductance path to minimize oscillations, enabling the circuit to maintain signal integrity even at high sampling rates where distortion would normally be problematic.
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 effectively reduces signal distortion, enhancing the accuracy of sampled values and improving the performance of switched capacitor ADCs by minimizing oscillations and maintaining the integrity of the input signal during sampling.
Implementation Method 1
charging a energy storage element to a value proportional to the input signal using a portion of charging energy received through a path having less lead inductance compared to the path connecting the input signal to the energy storage element
Data Source
AI summary
According to an aspect of the present invention, samples of an input signal are provided with reduced distortion, when the input signal is received from a lead terminal offering lead inductance on an input path. Such a feature is achieved by charging a energy storage element to a value proportional to the input signal using a portion of charging energy received through a path having less lead inductance compared to the path connecting the input signal to the energy storage element. Thus, the energy drawn through the lead impedance is reduced, thereby reducing the magnitude of the distortion caused.