Operational Amplifier Offset Compensation With Switched Feedback
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Solution Overview
Problem
Operational amplifiers in semiconductor integrated circuits often produce non-zero offset voltages due to design and fabrication errors, which are problematic in high-end electronics like TVs and mobile phones, leading to inefficiencies and increased power consumption.
Innovation Solution
The design of operational amplifiers that alternate between two operation periods, utilizing an input stage, amplification stage, output stage, voltage storage unit, and switching unit to control feedback paths, allowing for efficient compensation of offset voltages and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional operational amplifiers are used without offset compensation, then the circuit structure remains simple, but offset voltage errors accumulate and degrade performance
Solution Approach 1:
The operational amplifier is divided into two distinct operational periods: a first operation period for normal signal amplification and a second operation period for offset compensation. This temporal segmentation allows the circuit to perform both amplification and self-compensation functions without requiring entirely separate circuits, thus improving precision while controlling complexity.
Solution Approach 2:
The operational amplifier alternates between two operation periods in a periodic manner. During the second period, the switching unit reconfigures the feedback paths to enable offset compensation, while during the first period, normal amplification occurs. This periodic switching allows systematic offset elimination without continuous complexity.
2Measurement precision
If continuous offset compensation is implemented, then offset voltage accuracy improves, but power consumption increases
Solution Approach 1:
Offset compensation is performed periodically during the second operation period rather than continuously. The switching unit alternates between amplification mode and compensation mode, allowing the operational amplifier to reduce power consumption by disabling compensation circuits during the first operation period while maintaining precision through regular compensation cycles.
Solution Approach 2:
The feedback paths are dynamically reconfigured using switching units that change connectivity based on the operation period. During the second period, feedback paths are switched to enable offset compensation, while during the first period, paths are configured for normal operation. This dynamic switching optimizes power consumption by activating compensation only when needed.
3Measurement precision
If multiple feedback paths are added for offset compensation, then offset voltage accuracy improves, but circuit area increases
Solution Approach 1:
The same operational amplifier circuit and feedback paths serve dual purposes: normal signal amplification during the first operation period and offset compensation during the second operation period. The switching units enable the circuit to switch between these functions without requiring separate dedicated compensation circuits, thus improving precision while minimizing additional area.
Solution Approach 2:
The feedback paths are segmented into different configurations that are activated at different times. Rather than having all compensation paths active simultaneously (which would increase area), the circuit segments the operation into time periods where different feedback configurations are enabled, achieving compensation accuracy without proportional area increase.
Data Source
AI summary
An operational amplifier includes an input stage with a first main input unit, a first auxiliary input unit, a second main input unit and a second auxiliary input unit, an amplification stage with a first current mirror receiving currents from the first main input unit and the first auxiliary input unit, and a second current mirror receiving currents from the second main input unit and the second auxiliary input unit, an output stage receiving voltages from the first current mirror and the second current mirror, a voltage storage unit storing an intermediate voltage based on an output signal generated by the output stage during at least one of a first operation period and a second operation period, and a switching unit that differently controls a first feedback path between the output stage and the input stage and a second feedback path between the output stage to the voltage storage unit in accordance with the first operation period and the second operation period.