Programmable DAC Gain Stage With Leakage Current Compensation
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Solution Overview
Problem
Existing digital-to-analog converters (DACs) face issues with accuracy and integral non-linearity due to leakage current in the gain stage and ground disturbance when sharing a common ground with the gain stage.
Innovation Solution
Incorporating a leakage current control circuit and common ground control circuitry to stabilize the ground current, reducing leakage current and improving linearity by using a programmable gain stage with a variable gain network and operational amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a gain stage is included to improve the DAC's output range, then the output voltage range is improved, but leakage current in the gain stage degrades accuracy and integral non-linearity
Solution Approach 1:
A leakage current control circuit is introduced as an intermediary component between the gain stage and the DAC output. This circuit actively compensates for leakage currents by injecting equal and opposite currents, thereby eliminating the harmful effect of leakage on accuracy while preserving the gain stage's output range extension capability
Solution Approach 2:
The leakage current control circuit implements a feedback mechanism where leakage current is sensed and then compensated by generating a counteracting current. This closed-loop approach continuously maintains accuracy despite variations in leakage current, allowing the gain stage to operate at extended output ranges without sacrificing precision
2Device complexity
If the DAC and gain stage share a common ground to simplify circuit design, then device complexity is reduced, but ground disturbance degrades accuracy and integral non-linearity
Solution Approach 1:
The ground system is segmented into separate ground domains for the DAC and gain stage. Dedicated ground paths are provided for each functional block, preventing ground current from the gain stage from disturbing the DAC's reference potential. This segmentation maintains design simplicity while eliminating ground-induced accuracy degradation
Solution Approach 2:
Different ground quality requirements are applied to different parts of the circuit. The DAC section receives a clean, stable ground reference optimized for precision, while the gain stage has its own ground path optimized for handling higher currents. This localized ground strategy allows simplified overall design while maintaining high accuracy where needed
Data Source
AI summary
A circuit includes a digital-to-analog converter and a gain stage. The gain stage includes: an operational amplifier; a variable gain network; and a leakage current control circuit. A first input of the operational amplifier is coupled to an input of the gain stage. An output of the operational amplifier is coupled to an output of the gain stage. A first terminal of the variable gain network is coupled to the second input of the operational amplifier. A second terminal of the variable gain network is coupled to the output of the operational amplifier. A first terminal of the leakage current control circuit is coupled to the output of the operational amplifier. A second terminal of the leakage current control circuit coupled to a third terminal of the variable gain network.