Class-AB Amplifier Circuit With Cross-Coupled Current Mirrors
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Solution Overview
Problem
Existing amplifier circuits that combine low quiescent current with high gain and class-AB behavior often require complex additional stages and many transistors, increasing circuit area and supply current, while also being inefficient in controlling quiescent currents for low distortion.
Innovation Solution
An amplifier circuit with a differential input stage, two cross-coupled current mirrors, and a minimum selector circuit that eliminates the need for an extra intermediate stage, using a simple MOS minimum selector to control currents and achieve class-AB behavior, thereby reducing complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If feedback circuits with minimum selectors are used to control quiescent current accurately, then distortion performance is improved, but circuit complexity and transistor count increase
Solution Approach 1:
The patent combines the minimum selector circuit directly with the current mirror circuit, eliminating the need for separate feedback stages. The minimum selector shares transistors with the current mirror, merging two functions into a single integrated structure that reduces overall circuit complexity while maintaining accurate quiescent current control for low distortion performance
Solution Approach 2:
The current mirror transistors serve multiple functions: they act as both the current mirroring elements and the minimum selector components. This multi-functionality reduces the total transistor count while maintaining the ability to accurately control quiescent current and achieve class-AB behavior
2Adaptability or versatility
If extra stages are added for class-AB current control, then class-AB behavior is achieved, but circuit area and supply current increase
Solution Approach 1:
The patent merges the class-AB current control function into the existing current mirror structure by integrating the minimum selector. This eliminates the need for separate intermediate amplifier stages, reducing circuit area while maintaining accurate class-AB behavior through the shared transistor structure
Solution Approach 2:
The current mirror circuit automatically provides class-AB behavior through its inherent structure with the integrated minimum selector. The circuit self-regulates the quiescent current without requiring external control stages, reducing both area and supply current requirements while achieving the desired class-AB operation
3Measurement precision
If many transistors are used for minimum current comparison and differential signal conversion, then current control accuracy is improved, but power consumption increases
Solution Approach 1:
The patent merges the minimum current comparison function directly into the current mirror structure, eliminating separate comparison and conversion stages. The shared transistors perform multiple operations simultaneously, maintaining high current control accuracy while reducing the number of active devices and associated power consumption
Data Source
AI summary
An amplifier circuit, comprising a differential input stage (M1, M2), two cross-coupled current mirrors (M3, M4; M5, M6) coupled to respective outputs of the differential input stage (M1, M2), and a minimum selector circuit (M11, M12, M13, M14) coupled to outputs of the current mirrors.