Single-Ended DAC Capacitance Compensation for Harmonic Distortion
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Solution Overview
Problem
Single-ended current digital to analog converters (DACs) generate undesirable even harmonics due to capacitive feedback when activating current source transistors, leading to inefficiencies and increased power consumption.
Innovation Solution
Incorporating a capacitance circuit coupled with the gate and source terminals of the current source transistor to compensate for capacitive feedback, using a switch to connect the output terminal to the source terminal and a compensation capacitor to mitigate distortion caused by capacitive coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If single ended current DAC architecture is used to reduce power consumption, then power consumption is reduced, but even harmonics and distortion are generated due to capacitive feedback
Solution Approach 1:
A compensation capacitor is introduced as an intermediary element connected between the gate and source terminals of the current source transistor. This capacitor mediates the capacitive feedback effect by providing a compensating current path that cancels the harmful feedback, thereby eliminating even harmonics while preserving the low power consumption advantage of the single ended architecture
Solution Approach 2:
The patent applies feedback by connecting a compensation capacitor between the gate and source terminals of the current source transistor. This creates a feedback path that senses the capacitive coupling effect and generates a compensating signal to cancel the distortion, thereby improving linearity without increasing power consumption
2Power
If current source transistor is activated to generate current output, then current levels are generated, but nonlinearity and distortion occur due to capacitive feedback into the gate
Solution Approach 1:
The compensation capacitor acts as an intermediary that intercepts and compensates for the capacitive feedback signal before it can distort the gate voltage. This mediator element provides a corrective current path that maintains accurate current output levels while eliminating nonlinearity
Solution Approach 2:
The compensation capacitor is configured to provide preliminary anti-action by generating a compensating current that opposes and cancels the harmful capacitive feedback before it can affect the transistor operation. This preemptive compensation ensures linear current output without requiring complex post-processing
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
The solution effectively reduces distortion and odd-order harmonics, improving the linearity of the DAC output and reducing power consumption by compensating for capacitive feedback, thereby enhancing signal quality and efficiency.
Implementation Method 1
capacitive feedback into the gate of the current generating transistor when the cell is activated
Implementation Method 2
capacitance feedback between the gate terminal and the source terminal
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.