Single-Ended DAC Capacitive Compensation for Even Harmonics
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Solution Overview
Problem
Digital to analog converters (DACs) with single-ended current steering architectures face issues with power consumption and generate undesirable even harmonics due to capacitive feedback, which affects signal quality and efficiency.
Innovation Solution
The implementation of a capacitive compensation circuit across the source and gate terminals of the current source transistor in a single-ended DAC, using a capacitance circuit coupled with the output and gate terminals to counteract capacitive feedback, thereby reducing distortion and harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single-ended current DAC architecture is used to reduce power consumption, then power consumption is reduced, but capacitive feedback generates undesirable even harmonics that deteriorate signal quality
Solution Approach 1:
A compensation capacitor is introduced as an intermediary element between the output terminal and the gate terminal of the current generating transistor. This capacitor mediates the capacitive feedback effect by providing an alternative path for the feedback current, thereby canceling the harmful even harmonics generated by the intrinsic gate-drain capacitance of the transistor while maintaining the low power consumption benefits of the single-ended architecture
2Productivity
If multiple cells of current generating transistors are activated in a single-ended DAC, then the DAC functionality is achieved, but capacitive feedback into the gate terminal causes distortion and even harmonics
Solution Approach 1:
The compensation capacitor acts as a mediator that is selectively connected to the gate terminal of each current generating transistor through switches. When a transistor cell is activated, the compensation capacitor is connected in parallel with the transistor's gate-drain capacitance, providing a nullifying effect that cancels the capacitive feedback and eliminates distortion while allowing the transistor to function properly as part of the DAC
3Object-generated harmful factors
If a differential architecture is used to improve signal quality, then signal quality is improved, but power consumption increases significantly
Solution Approach 1:
The invention converts the harmful capacitive feedback effect inherent in single-ended architecture into a beneficial condition by introducing a compensation capacitor that exploits the same capacitive coupling mechanism. The compensation capacitor is sized and connected such that its capacitive effect opposes and cancels the harmful feedback capacitance, thereby eliminating even harmonics and improving signal quality while maintaining the low power consumption advantage of single-ended operation
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 reduces capacitive coupling effects, leading to improved signal quality and reduced power consumption by minimizing the generation of unwanted harmonics and enhancing the efficiency of the DAC's output.
Implementation Method 1
capacitive feedback into the gate of the current generating transistor when the cell is activated
Data Source
AI summary
This disclosure relates to a compensating for nonlinearity resulting from a capacitance feedback in current cells of a single ended digital to analog circuit.