Proportional-to-Supply Current Generator Circuit Area Reduction
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Solution Overview
Problem
Existing current generators that produce a current proportional to the power supply voltage require significant circuit area due to the need for complex operational amplifiers and bias circuits, which are resource-intensive and consume substantial space.
Innovation Solution
A current generator design that utilizes two current generators providing currents proportional to the difference between a power supply voltage and a gate-to-source voltage, with these currents summed to produce an output current proportional to the power supply voltage, eliminating the need for large operational amplifiers and complex bias circuits by using MOS transistors and resistors in a current mirror configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage divider and operational amplifier are used to generate a proportional-to-supply current, then the current tracking accuracy is improved, but the circuit area increases substantially
Solution Approach 1:
The patent extracts and eliminates the operational amplifier from the circuit by using a direct transistor biasing approach. The proportional-to-supply current is generated through a simplified path using only resistors and transistors, removing the complex op-amp-based transconductance loop while maintaining current tracking functionality.
Solution Approach 2:
The patent replaces the expensive and area-intensive operational amplifier with inexpensive, compact passive components (resistors) and simple active devices (transistors). This substitution achieves the same functional goal with significantly reduced circuit area and component complexity.
2Measurement precision
If operational amplifiers are used in the current generator, then the current proportionality to power supply voltage is achieved, but the device complexity increases
Solution Approach 1:
The patent segments the current generation function into separate, simple stages: voltage division through resistors, transistor biasing, and current mirroring. Each stage performs a single, well-defined function, eliminating the need for a complex integrated operational amplifier while maintaining overall current proportionality to the power supply voltage.
Solution Approach 2:
Instead of using an operational amplifier to actively regulate and force current proportionality, the patent inverts the approach by using passive resistor-divider networks and transistor characteristics to naturally establish the proportional relationship. The circuit lets the physics of the components dictate the proportional behavior rather than actively controlling it.
Data Source
AI summary
A current generator includes first and second current generators and an output current generator. The first current generator has an output for providing a first current, the first current proportional to a difference between a first power supply voltage and a first gate-to-source voltage. The second current generator has an output for providing a second current, the second current proportional to a second gate-to-source voltage. The second gate-to-source voltage is approximately equal to the first gate-to-source voltage. The output current generator provides an output current proportional to a sum of said first current and said second current.