Operational Amplifier Current Mirror Layout for Low Quiescent Current
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Solution Overview
Problem
Existing operational amplifiers have a large quiescent current under no load conditions and require complex circuitry with multiple differential pairs, which is inefficient in terms of power consumption and component count.
Innovation Solution
A semiconductor operational amplifier design featuring a single differential pair and a current source configuration that controls quiescent current as a ratio of the bias current, allowing for a large output voltage swing and current supply while minimizing quiescent current through a current mirror configuration, thereby reducing power dissipation and component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple differential pairs are used to increase output current capability, then the current supply capacity is improved, but the device complexity and quiescent current increase
Solution Approach 1:
The patent combines multiple differential pairs into a single differential pair configuration. The first and second operational amplifiers share a common differential pair (third and fourth transistors), merging their input stages. This consolidation reduces the total transistor count from what would be required for separate amplifiers, lowering device complexity while maintaining the ability to drive multiple outputs with appropriate current mirroring
2Power
If multiple differential pairs are used to increase output current supply, then the current capability is improved, but the quiescent current increases
Solution Approach 1:
The patent merges the input stages of multiple operational amplifiers into a single shared differential pair. The current from the current source is split between the first and second amplifiers through current mirroring, but the quiescent current flows through only one differential pair instead of multiple separate pairs, significantly reducing the total quiescent power consumption while maintaining output current capability
Solution Approach 2:
The shared differential pair serves multiple functions by being the input stage for both the first and second operational amplifiers. This single differential pair structure provides the voltage-to-current conversion for multiple output stages, making the circuit more efficient by eliminating redundant input stages that would each consume quiescent current
3Use of energy by moving object
If a single differential pair is used to reduce quiescent current, then power consumption is improved, but the output current supply capability may be limited
Solution Approach 1:
The patent uses current mirror circuits to create copies of the current from the single differential pair. The current generated by the shared differential pair is mirrored to multiple output stages through current mirror transistors, allowing a single current-generating element to supply multiple outputs with appropriate current levels without requiring multiple differential pairs
Data Source
AI summary
In one aspect, an operational amplifier is configured to form a quiescent current that is a ratio of a current of a current source of the operational amplifier and to provide a load current to a load that is not ratioed to the current of the current source.