Analog Track-and-Hold with First-Order Extrapolation
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Solution Overview
Problem
Zeroth-order track-and-hold circuits introduce dynamic errors when the input signal changes significantly during the hold phase, and filtering methods often introduce delay, which complicates signal reconstruction and processing.
Innovation Solution
Implementing a first-order extrapolation technique using an electronic circuit with an analog amplifier and storage circuit, which stores the input signal and its slew rate, allowing the output to be linearly extrapolated during the hold phase, reducing the need for digital signal processing and simplifying circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If zeroth-order track-and-hold is used to hold the output constant during the hold phase, then the circuit implementation is simple, but dynamic errors increase when the input signal changes significantly
Solution Approach 1:
The patent changes the hold mode parameter from constant output (zeroth-order) to linearly varying output (first-order) by introducing a slew rate term. This allows the output to track the input signal's rate of change, significantly reducing dynamic errors while maintaining analog circuit implementation
Solution Approach 2:
The patent transitions from a static hold mode (constant output) to a dynamic hold mode where the output varies linearly with time based on the stored slew rate. This dynamic approach allows the circuit to adapt to signal changes during the hold phase, improving accuracy without increasing complexity
2Measurement precision
If filtering is applied to reduce transients and improve signal reconstruction, then signal accuracy improves, but response time increases due to delay
Solution Approach 1:
The patent performs preliminary action by capturing and storing the slew rate information at the end of the track phase before the hold phase begins. This pre-captured rate information is then used during the hold phase to predict signal behavior, eliminating the need for post-processing filtering and reducing delay
3Area of stationary object
If zeroth-order track-and-hold is used, then the circuit die area is smaller, but filtering complexity must increase to maintain accuracy
Solution Approach 1:
The patent merges the track-and-hold function with first-order extrapolation capability in a single analog circuit implementation. By combining the storage of input signal samples with slew rate information and using an operational amplifier to perform linear extrapolation, the circuit achieves improved accuracy without requiring separate filtering stages, thus maintaining small die area
Data Source
AI summary
A dynamic error introduced by track-and-hold circuits can be reduced by using an input signal derivative to perform linear extrapolation during the hold period, allowing the output of the track-and-hold circuit to provide improved performance in reconstructing an undistorted input waveform, or to perform other applications such as demultiplexing. As described herein, a track-and-hold circuit and related techniques can include use of a first-order (e.g., linear) extrapolation. A first-order extrapolation can better approximate or reconstruct a signal during a specified hold duration, as compared to a zeroth-order technique. Use of analog circuits to implement the first-order extrapolation can one or more of reduce complexity of a circuit implementation or improve performance, such as by not requiring digital signal processing circuitry in performing the extrapolation.