Balanced Offset Compensation Circuit for Differential Amplifiers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional offset compensation techniques for differential amplifiers suffer from unbalanced leakage currents, leading to accumulation of differential voltage on input terminals and circuit malfunction, especially during long compensation periods, and require disabling the input signal during auto-zeroing phases, limiting continuous time operation.
Innovation Solution
The implementation of three switches between each input and output of the differential amplifier, which are controlled to reduce differential degradation by opening and closing combinations during auto-zeroing and operation phases, ensuring balanced biasing and minimizing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the input offset voltage is stored across a series capacitor during an auto-zeroing phase, then the input offset voltage compensation is achieved, but unbalanced leakage currents cause accumulation of differential voltage on the amplifier input terminals over time resulting in circuit malfunction
Solution Approach 1:
The patent introduces asymmetry by adding a leakage compensation circuit that is selectively activated during the auto-zeroing phase. This compensation circuit intentionally creates an unbalanced path to counteract the unbalanced leakage currents, thereby preventing differential voltage accumulation while maintaining effective offset compensation.
Solution Approach 2:
The leakage compensation circuit acts as an intermediary element between the series capacitor and the amplifier input terminals. It mediates the harmful effect of leakage currents by providing a compensating current path that balances the overall circuit behavior during the compensation phase.
2Measurement precision
If switching circuits are closed to configure the differential amplifier as a unity gain buffer during auto-zeroing phase, then offset compensation is achieved, but the input signal must be disabled during this phase limiting continuous time operation
Solution Approach 1:
The patent segments the operation into distinct phases (auto-zeroing phase and signal processing phase) using switching circuits. During the auto-zeroing phase, the amplifier is configured as a unity gain buffer for offset compensation, while during the signal processing phase, the amplifier processes input signals. This segmentation allows each phase to optimize its function without interfering with the other.
Solution Approach 2:
The patent implements periodic switching between auto-zeroing and signal processing phases. The switching circuits are controlled to periodically alternate between closing (for offset compensation) and opening (for signal processing), enabling the system to achieve both accurate offset compensation and continuous time operation through rhythmic phase transitions.
Data Source
AI summary
Balanced offset compensation is provided for a differential amplifier circuit. Two sets of three switches are employed between respective inputs and outputs of the differential amplifier to shunt the outputs to the input terminals during auto-zeroing phase. By opening and closing different combinations of the switches during auto-zeroing and operation phases, differential degradation due to unbalanced leakage currents is substantially reduced.