Follow-Hold Sampling Switch with Common-Mode Bootstrap Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional gate-voltage-bootstrap sampling switches face challenges in maintaining high linearity, especially with large input signals, due to high gate voltages that can lead to reliability issues and undesired leakage currents, making it difficult to meet requirements for high-speed and large input signal applications.
Innovation Solution
A follow-hold switch circuit comprising a follower, sampling sub-circuit, bootstrap-control sub-circuit, and sampling-switch-control sub-circuit, where a bootstrap capacitor is used to provide a common-mode voltage during the holding state, improving linearity and reducing circuit complexity by eliminating the need for multiple capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional gate-voltage-bootstrap sampling switch is used, then high linearity can be maintained for small input signals, but gate voltage becomes too high for large input signals causing reliability issues and leakage current
Solution Approach 1:
The patent divides the sampling switch into two separate NMOS transistors (first sampling switch and second sampling switch) with different gate voltage control mechanisms. The first sampling switch uses traditional bootstrap control while the second uses common-mode voltage control, allowing each to operate in its optimal voltage range and collectively cover the full input signal dynamic range without excessive gate voltages
Solution Approach 2:
The patent dynamically switches between two different sampling switch configurations based on input signal amplitude. For small signals, the first sampling switch with bootstrap control is used; for large signals, the second sampling switch with common-mode voltage control is used, optimizing performance across the entire signal range while preventing reliability issues
2Manufacturing precision
If traditional gate-voltage-bootstrap sampling switch is used, then high linearity can be achieved, but circuit complexity increases due to multiple capacitors
Solution Approach 1:
The patent extracts and eliminates the bootstrap capacitor from the circuit by replacing the traditional gate-voltage-bootstrap mechanism with a common-mode voltage control approach for the second sampling switch. This removes the need for multiple capacitors while maintaining high linearity through the dual-switch architecture
Solution Approach 2:
The patent makes the common-mode voltage node serve multiple functions: it provides the gate voltage for the second sampling switch, acts as a reference for the differential pair, and eliminates the need for separate bootstrap capacitor circuits. This multi-functionality reduces overall circuit complexity while preserving linearity performance
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 proposed circuit enhances linearity and reduces circuit area and cost by maintaining a common-mode voltage during the holding state, improving spurious-free dynamic range (SFDR) and signal noise distortion ratio (SNDR) compared to traditional structures.
Implementation Method 1
a bootstrap capacitor in the bootstrap-control sub-circuit
Implementation Method 2
the follower is connected to an output of the sampling sub-circuit
Data Source
AI summary
A follow-hold switch circuit comprising: a follower; a sampling sub-circuit for voltage sampling; a bootstrap-control sub-circuit, which provides a bootstrap voltage to the sampling sub-circuit when the circuit is in a following state; a sampling-switch-control sub-circuit, which provides a common-mode voltage to a bootstrap capacitor in the bootstrap-control sub-circuit when the circuit is in a holding state; the follower is connected to an output of the sampling sub-circuit; the sampling sub-circuit is connected to the bootstrap-control sub-circuit and the sampling-switch-control sub-circuit respectively through a sampling switch; the present disclosure can effectively improve the linearity of sampling switches.