Compensated Current Mirror for Low-Voltage Matching Accuracy
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Solution Overview
Problem
As power supply voltages decrease in metal-oxide semiconductor (MOS) fabrication, current mirrors experience degradation in mirroring effect due to low headroom, leading to significant current mismatches at higher output voltages and channel modulation effects at lower voltages.
Innovation Solution
The implementation of a current mirror system with two switches and two compensation circuits, where the first compensation circuit adjusts the drain voltage of one switch based on the drain voltage of the other, and the second compensation circuit adjusts the current through one switch based on the drain voltage of the second switch, maintaining current matching across a wider range of output voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If power supply voltage is decreased to advance MOS fabrication technology, then manufacturing precision is improved, but current mirror accuracy deteriorates due to low headroom
Solution Approach 1:
The patent implements feedback mechanisms where compensation circuits continuously monitor drain voltages and adjust their operating points accordingly. The first compensation circuit receives feedback about the second switch's drain voltage and adjusts its own drain voltage in response, creating a closed-loop system that maintains current mirror accuracy despite low supply voltage conditions
Solution Approach 2:
The patent dynamically changes operating parameters (drain voltages) of the compensation circuits based on real-time conditions. By adjusting drain voltages of the compensation circuits in response to each other, the system adapts to low headroom conditions while maintaining accurate current mirroring across a wide output voltage range
2Adaptability or versatility
If output voltage increases, then current mirror range is extended, but current mismatch increases due to channel modulation effects
Solution Approach 1:
The compensation circuits employ feedback mechanisms where each circuit monitors the drain voltage of the other and adjusts its operating point in response. This continuous feedback loop counteracts channel modulation effects that would otherwise cause current mismatches at higher output voltages, enabling accurate current mirroring from 0V to 1.7V
Solution Approach 2:
The patent makes the compensation circuits dynamic by allowing their drain voltages to adjust in real-time based on the operating conditions. This dynamic adjustment capability enables the current mirror to maintain accuracy across a wide output voltage range, adapting to both low and high voltage conditions without significant current mismatch
Data Source
AI summary
Some embodiments of the system comprise a current mirror with two switches (a first switch and a second switch) and two compensation circuits (a first compensation circuit and a second compensation circuit). In one embodiment, the first compensation circuit adjusts a drain voltage of the second switch based on a drain voltage of the first switch, and the second compensation circuit adjusts a current through the first switch based on the drain voltage of the second switch.