Current Mirror Switch Circuit for Off-Leak Current Suppression
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Solution Overview
Problem
Current-variable current mirror circuits face significant errors due to off-leak currents, particularly in binary-weighted configurations, as the gate length of transistors shrinks, leading to increased off-time leak currents and errors in current ratios.
Innovation Solution
The proposed current mirror circuit incorporates a switch circuit with specific transistor configurations and an inverter circuit to control the on/off states of transistors, ensuring that the off-leak current flows through different paths, reducing errors by maintaining transistors in deep reverse off states, thereby minimizing leak currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If transistors are shrunk to reduce circuit size, then integration density is improved, but off-time leak current increases
Solution Approach 1:
A fifth transistor of opposite conductivity type is introduced as an intermediary element to actively control and suppress the off-leak current of the switch transistors. This mediator transistor creates a counteracting current path that prevents the harmful leak current from affecting the main signal path, thereby resolving the contradiction between miniaturization and leak current suppression.
Solution Approach 2:
The invention changes the operational parameters of the transistor by utilizing deep reverse off state conditions. By controlling the voltage parameters and biasing conditions, the fifth transistor forces the switch transistors into a deep reverse off state, significantly reducing their off-leak current despite the reduced gate length. This parameter change allows continued scaling while maintaining low leak current.
2Measurement precision
If switches are turned off to control current gain, then current ratio precision is improved, but off-leak current error increases
Solution Approach 1:
The invention converts the harmful off-leak current into a beneficial effect by using the fifth transistor to create a counteracting current. The leak current that would normally cause error is now compensated for by the opposite-polarity transistor, turning the harmful factor into an opportunity for active cancellation and achieving both high precision and low error.
Solution Approach 2:
The fifth transistor provides a feedback mechanism that actively monitors and compensates for off-leak current effects. By continuously maintaining the switch transistors in deep reverse off state through the action of the fifth transistor, the system dynamically corrects for leak current variations, ensuring both precision and reliability are maintained simultaneously.
Data Source
AI summary
A current mirror circuit includes: a plurality of first transistors connected to a first power supply at their sources and to an input terminal at their gates and drains; and a second transistor connected to the first power supply at its source, to the input terminal at its gate, and to an output terminal at its drain. A switch circuit is provided between at least one of the first transistors and the input terminal. The switch circuit includes third and fourth transistors connected in series between the first transistor and the input terminal, an inverter circuit, and a fifth transistor connected between a middle node of the third and fourth transistors and an 10 output terminal of the inverter circuit. A switch control signal is given to the gates of the third to fifth transistors and to the input of the inverter circuit.