Amplifier Input Shielding via Internal Node for Parasitic Mismatch
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Solution Overview
Problem
Switched capacitor circuits, such as those used in analog-to-digital converters, are vulnerable to parasitic capacitances at the input of amplifiers, leading to accuracy issues due to mismatched capacitance values, which result in gain errors and integral non-linearity errors.
Innovation Solution
The implementation of shielding that is connected to an internal node of the amplifier rather than a reference node, effectively reducing the impact of parasitic capacitances by placing them in parallel with the gate-source capacitance, thereby reducing the parasitic wiring capacitance mismatch and improving the feedback factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If shielding is connected to a reference node, then the shielding provides electrostatic protection, but parasitic wiring capacitance mismatch occurs at the amplifier inputs
Solution Approach 1:
The patent introduces an intermediary node within the differential amplifier circuit that serves as a connection point for the shielding. This intermediary node acts as a mediator that allows the shielding to be connected to the amplifier inputs without creating parasitic wiring capacitance mismatch, thereby resolving the contradiction between providing electrostatic protection and maintaining measurement precision.
Solution Approach 2:
The patent applies the equipotentiality principle by connecting the shielding to nodes that maintain equal potential relationships within the differential amplifier. This ensures that the shielding provides electrostatic protection while maintaining balanced capacitance values at the amplifier inputs, preventing gain errors caused by capacitance mismatch.
2Object-affected harmful factors
If shielding is connected to a reference node, then the shielding reduces electromagnetic interference, but the parasitic wiring capacitance causes integral non-linearity errors
Solution Approach 1:
The patent uses an intermediary node within the differential amplifier as a mediation point for the shielding connection. This intermediary structure allows the shielding to effectively reduce electromagnetic interference while avoiding the creation of unbalanced parasitic capacitances that would cause integral non-linearity errors.
Solution Approach 2:
By connecting the shielding to equipotential nodes within the differential amplifier, the patent ensures that electromagnetic interference is reduced while the parasitic capacitances remain balanced. This maintains the symmetry of the differential input stage, preventing integral non-linearity errors.
3Device complexity
If traditional shielding connection is used, then the circuit structure is simple, but the feedback factor is reduced due to parasitic capacitance mismatch
Solution Approach 1:
The patent introduces an intermediary connection structure within the differential amplifier that serves as a mediator between the shielding and the amplifier inputs. This intermediary node maintains the simplicity of the overall circuit structure while ensuring that the shielding connection does not create parasitic capacitance mismatch, thereby preserving the feedback factor and reliability.
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 significantly reduces gain errors and integral non-linearity errors, enhancing the accuracy and performance of the circuit by minimizing the effects of parasitic capacitances, meeting the requirements for higher bit-resolution ADCs.
Implementation Method 1
Parasitic capacitances are often found at the input(s) to an amplifier and, more particularly, between the input(s) of the amplifier and a static reference node
Data Source
AI summary
A circuit includes an amplifier including a differential input stage including a first input terminal and a second input terminal. The circuit further includes a differential input line coupled to the first input terminal and the second input terminal, and shielding at least partially encompassing the differential input line. The shielding is connected to a node of the differential input stage of the amplifier.