Bootstrap Sampling Network Circuit for MOSFET Back-Gate Linearity
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Solution Overview
Problem
Sampling networks face distortion issues due to back-gate capacitance of MOSFET devices, which are not adequately addressed by existing solutions like bootstrap circuits that introduce unwanted nonlinearity and residual effects.
Innovation Solution
An integrated circuit with additional series resistance is introduced between the input and back-gate switch of the sampling network, using a pair of bootstrap circuits and a resistive element to reduce nonlinearity and distortion by maintaining a constant gate-to-source voltage and isolating the back-gate from input signal variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bootstrap circuit is used to eliminate resistance variation, then linearity is improved, but unwanted junction capacitance is introduced at the input
Solution Approach 1:
The patent extracts and removes the back-gate connection from the input signal path by using a separate bootstrap circuit configuration. The back-gate is bootstrapped independently without being directly connected to the input, thereby eliminating the harmful junction capacitance while preserving the linearity benefits of bootstrapping.
Solution Approach 2:
The patent segments the bootstrap function into separate components: one bootstrap circuit for the gate and another for the back-gate. This segmentation allows independent optimization of each bootstrap path, enabling the back-gate to be bootstrapped without introducing unwanted capacitance at the input node.
2Reliability
If back-gate bootstrapping is applied to reduce distortion, then resistance variation is reduced, but additional nonlinearity is introduced at the input
Solution Approach 1:
The patent introduces an intermediary bootstrap circuit configuration that mediates between the back-gate and the input signal. The back-gate is bootstrapped through a dedicated circuit path that does not directly couple to the input, acting as an intermediary that provides resistance stability without introducing nonlinearity at the input node.
3Measurement precision
If standard bootstrap circuit is used, then switch resistance variation is reduced, but residual distortion effects remain
Solution Approach 1:
The patent employs dynamic bootstrapping where the bootstrap voltage is actively maintained to track signal variations. This dynamic approach allows the circuit to adapt to changing conditions, reducing resistance variation more effectively than static bootstrapping while minimizing residual distortion through active compensation.
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 solution effectively decreases nonlinearity and distortion at the input of the sampling network, improving its performance by converting capacitive high-pass filters to low-pass filters and reducing relative distortion, while maintaining the benefits of bootstrap circuits without introducing additional capacitance.
Implementation Method 1
An integrated circuit with additional series resistance is introduced between the input and back-gate switch of the sampling network, using a pair of bootstrap circuits and a resistive element to reduce nonlinearity and distortion
Implementation Method 2
A bootstrap circuit that is connected to an input switch can pull up the current through the input switch and keep the gate-to-source and the back-gate-to-source voltages constant, and effectively eliminate a variation of the resistance of the nonlinear resistor
Data Source
AI summary
An integrated circuit allows for the correction of distortion at an input of a sampling network. The integrated circuit contains a first bootstrap circuit to drive a sampling network transistor and a second bootstrap circuit to separate the back-gate terminal of the transistor from a voltage input by a resistance inserted in series. The presence of the inserted resistance counteracts the effect of the nonlinear back-gate capacitance on the distortion at the input.