Bootstrap Analog Multiplexer for Low-Harmonic MOS Switching
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Solution Overview
Problem
Analog multiplexers with metal-oxide-silicon (MOS) transistors introduce harmonics into the output signal due to varying resistance when the transistor is enabled, which is undesirable.
Innovation Solution
The multiplexer employs two bootstrap circuits coupled to the source and gate terminals of the transistor, operating in alternate phases to maintain a constant gate-to-source voltage (VGS), ensuring a constant resistance of the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an MOS transistor is used as a switch in the multiplexer, then the multiplexer can pass high frequency analog input signals, but the varying resistance of the transistor introduces harmonics into the output signal
Solution Approach 1:
The patent changes the electrical parameters of the MOS transistor by maintaining a constant gate-to-source voltage (VGS) through bootstrap circuits. This parameter control ensures the transistor operates in a linear region with constant resistance, eliminating harmonic distortion while maintaining signal passing capability
Solution Approach 2:
The bootstrap circuits perform preliminary action by pre-charging capacitors to establish the required gate voltage before the switch closes. This ensures the transistor is already in the desired operating state with constant resistance before signal transmission begins
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 prevents the introduction of harmonics into the output signal, allowing for reliable signal transmission without distortion.
Implementation Method 1
The two bootstrap circuits operate in alternate phases to maintain the constant VGS through operation
Data Source
AI summary
A multiplexer includes an input, an output, and a main switch configured to pass a signal from the input to the output. The multiplexer includes two bootstrap circuits that collectively maintain a constant voltage between terminals of the main switch during alternating phases.