Tri-State Buffer Switch Control for Variable Impedance Gain Nodes
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Solution Overview
Problem
Traditional approaches to designing variable impedance elements in audio device circuits, such as those used in personal audio devices, often lead to overstressing of gate nodes as device feature sizes shrink, due to the use of series-coupled resistive elements with gain switches.
Innovation Solution
A system with an impedance selector and two switches controlling a varying voltage node, utilizing a tri-state buffer with a p-type and n-type field effect transistor inverter, and a second n-type transistor to enable or disable the buffer responsive to an enable signal, placing the output in a high-impedance state when disabled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If series-coupled resistive elements with gain switches are used to implement variable impedance, then gain control capability is achieved, but gate nodes of gain switches are overstressed especially as device feature sizes shrink
Solution Approach 1:
The patent segments the variable impedance control into two independent switches (first switch and second switch) that operate on different voltage nodes. The first switch controls a first voltage node while the second switch controls a second voltage node, dividing the control function to reduce stress on individual gate nodes compared to a single switch approach.
Solution Approach 2:
The patent changes the voltage parameters by introducing different voltage levels (first voltage and second voltage) at different nodes. By maintaining different voltage potentials at the first and second voltage nodes, the patent reduces the voltage swing and stress on individual switch gate nodes while preserving the overall variable impedance functionality.
2Device complexity
If device feature sizes shrink to improve integration, then device density increases, but gate nodes become more susceptible to overstress
Solution Approach 1:
The control function is segmented into two independent switch circuits that operate separately. This segmentation allows each switch to handle smaller voltage swings and reduced stress, making the design more robust as feature sizes shrink and integration increases.
Solution Approach 2:
The patent introduces an intermediary approach by using two switches with different voltage nodes as intermediate control points. This intermediary structure distributes the stress across multiple components rather than concentrating it on a single gate node, improving reliability in scaled-down devices.
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 configuration reduces the disadvantages of existing approaches by effectively controlling variable impedance, minimizing stress on gate nodes and allowing for precise gain adjustment in audio device amplifiers.
Implementation Method 1
an inverter comprising a p-type field effect transistor in series with an n-type field effect transistor and configured to generate the output signal as a function of the input signal when the tri-state buffer is enabled
Implementation Method 2
a second n-type field effect transistor coupled in series between the p-type field effect transistor and a source voltage of the tri-state buffer such that a cathode of a body diode of the second n-type field effect transistor and a cathode of a body diode of the p-type field effect transistor share a common electrical node, wherein the second n-type field effect transistor is configured to selectively enable and disable the tri-state buffer responsive to an enable signal received at a gate of the second n-type field effect transistor
Implementation Method 3
a cathode of a body diode of the second n-type field effect transistor and a cathode of a body diode of the p-type field effect transistor share a common electrical node
Data Source
AI summary
In accordance with embodiments of the present disclosure, a system may include a buffer and a switch coupled between the buffer and a voltage supply such that the switch controls a varying voltage at a varying voltage node coupled to the buffer.