Body-Biased Bootstrapped Switch for Linear Signal Sampling
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Solution Overview
Problem
Existing bootstrapped switches are unable to meet linearity requirements due to the impact of voltage-dependent parasitic capacitors, which cause nonlinear distortion in signal conversion.
Innovation Solution
A bootstrapped switch design incorporating a sampling transistor, a bootstrapped circuit, and a buffer circuit that uses body biasing to maintain a constant voltage difference between the control node and the sampling transistor, reducing the impact of voltage-dependent capacitors by generating a buffer signal to drive the transistor body instead of the input signal directly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bootstrapped switch is used to provide stable turn-on resistance, then linearity is improved, but voltage-dependent parasitic capacitor impacts still degrade performance
Solution Approach 1:
The patent changes the voltage parameter by applying a boosted voltage to the body terminal of the sampling transistor through a bootstrapped circuit. This voltage transformation maintains a constant voltage difference between gate and source terminals, thereby stabilizing the turn-on resistance and reducing the impact of voltage-dependent parasitic capacitors on linearity
Solution Approach 2:
The patent introduces a buffer circuit as an intermediary component that generates a buffered version of the input signal to drive the body terminal. This intermediary buffer signal isolates the direct connection between input signal and body terminal, reducing the harmful effects of voltage-dependent parasitic capacitors while maintaining signal integrity
2Manufacturing precision
If body biasing is applied to reduce parasitic capacitor impacts, then linearity is improved, but additional circuit components increase device complexity
Solution Approach 1:
The bootstrapped circuit serves multiple functions: it boosts the body terminal voltage, maintains constant gate-source voltage difference, and reduces parasitic capacitor effects. By combining these functions into a single circuit structure, the patent achieves improved linearity without proportionally increasing device complexity
Solution Approach 2:
The patent merges the body biasing function with the existing bootstrapped switch structure. The buffer circuit is integrated into the overall switch architecture, and the body terminal voltage control is combined with the gate control mechanism, thereby achieving enhanced linearity while minimizing additional complexity
Data Source
AI summary
A bootstrapped switch includes a sampling transistor, a bootstrapped circuit, and a buffer circuit. The sampling transistor is configured to be selectively turned on according to a level of a control node, in order to transmit an input signal from a first terminal of the sampling transistor to a second terminal of the sampling transistor, in which a body of the sampling transistor is configured to receive a buffer signal. The bootstrapped circuit is configured to pull up the level of the control node, such that a constant voltage difference is present between the control node and the first terminal of the sampling transistor during a turn-on interval of the sampling transistor. The buffer circuit is configured to generate the buffer signal according to the input signal.