MOS Current Mirror With Push-Pull Stage for Stable Voltage Swing
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Solution Overview
Problem
Existing MOS-based current mirror circuits require multiple 'ideal' reference current sources and struggle with high output impedance and voltage swing stability, particularly in low-dropout voltage regulators.
Innovation Solution
The proposed electronic circuit incorporates a reference current terminal, an MOS current mirror stage with equal gate-to-source voltage mirroring MOS devices, and an MOS push-pull amplifier stage configured with multiple pairs of MOS devices, which allows for scalable output current and improved impedance and voltage swing without an operational amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional MOS-based current mirror circuits are used, then the circuit structure is simple, but the output impedance is low and voltage swing stability is poor
Solution Approach 1:
The current mirror circuit is divided into multiple functional stages: a basic MOS current mirror stage for current replication, a push-pull amplifier stage for voltage swing enhancement, and a current mode amplifier stage for impedance boosting. Each stage performs a specific function, allowing the overall circuit to achieve high output impedance and voltage swing stability without excessive complexity.
Solution Approach 2:
The patent combines three different circuit configurations (current mirror, push-pull amplifier, and current mode amplifier) into a single integrated circuit. This merging of functions allows the circuit to simultaneously achieve current mirroring, high voltage swing, and high output impedance that would be difficult to obtain with any single configuration alone.
2Reliability
If multiple reference current sources are used to improve stability, then the output impedance improves, but the device complexity increases
Solution Approach 1:
The push-pull amplifier stage serves multiple functions simultaneously: it provides voltage swing enhancement, acts as an impedance transformation stage, and works with the current mirror to achieve current replication. This multi-functionality reduces the need for separate dedicated reference current sources for different purposes.
Solution Approach 2:
The current mode amplifier stage incorporates feedback mechanisms that automatically adjust the operating point and maintain stability. This feedback control allows the circuit to achieve stable operation with a single reference current source, as the feedback loop compensates for variations and maintains the desired output characteristics.
3Reliability
If an operational amplifier is used to improve voltage swing stability, then the voltage swing stability improves, but the device complexity and power consumption increase
Solution Approach 1:
The patent replaces the expensive and complex operational amplifier with a simpler push-pull amplifier stage using standard MOS devices. While operational amplifiers provide good stability, they consume more power and occupy more area. The push-pull configuration achieves comparable stability with lower cost and power consumption, suitable for integrated circuit applications.
Solution Approach 2:
The patent substitutes the voltage-mode operation of traditional operational amplifiers with a current-mode operation in the push-pull amplifier stage. This substitution allows the circuit to achieve voltage swing stability through current control mechanisms rather than voltage feedback, reducing the need for high-gain operational amplifiers and their associated complexity.
Data Source
AI summary
The present disclosure provides an electronic circuit having one reference current terminal arranged to connect to a reference current generator, an MOS current mirror stage, an MOS push-pull amplifier stage operatively coupled to the current mirror stage and the current mode amplifier stage.