Native MOSFET Current Reference Circuit Eliminates Start-Up Logic
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Solution Overview
Problem
Current reference circuits in analog integrated circuits require start-up circuitry to initiate current flow, increasing power consumption and circuit size, which is undesirable for low-power applications.
Innovation Solution
The development of current reference circuits that include native MOSFETs and negative feedback amplifiers, eliminating the need for start-up circuitry by utilizing transistors with varying threshold voltages to self-initiate current flow, thereby reducing power consumption and circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If start-up circuitry is added to initiate current flow, then current reference generation is enabled, but power consumption and circuit area increase
Solution Approach 1:
The patent removes the start-up circuitry from the current reference circuit by exploiting the inherent threshold voltage differences between native MOSFETs and standard MOSFETs. The native MOSFET's naturally lower threshold voltage enables it to turn on first and initiate current flow without requiring external start-up circuitry, thus extracting the unnecessary start-up components while maintaining reliable current reference generation.
Solution Approach 2:
The circuit uses the native MOSFET's own threshold voltage characteristics to self-initiate current flow. The native MOSFET automatically turns on before standard MOSFETs due to its lower threshold voltage, creating the initial current without external assistance. This self-service mechanism eliminates the need for separate start-up circuitry that would otherwise be required to kick-start the current reference generation.
2Reliability
If start-up circuitry is added to initiate current flow, then current reference generation is enabled, but circuit area increases
Solution Approach 1:
The patent extracts and removes the start-up circuitry from the overall circuit design by relying on the native MOSFET's inherent properties. This elimination of external start-up components directly reduces the total circuit area while maintaining the ability to generate current reference, as the native MOSFET itself performs the start-up function through its threshold voltage characteristics.
3Device complexity
If native MOSFETs with varying threshold voltages are used, then start-up circuitry is eliminated, but manufacturing precision requirements increase
Solution Approach 1:
The patent exploits the natural parameter difference in threshold voltages between native MOSFETs and standard MOSFETs. By designing the circuit to rely on this inherent parameter variation rather than requiring precise threshold voltage control, the approach simplifies the overall device complexity while accepting that manufacturing processes must maintain reasonable threshold voltage characteristics. The circuit topology is specifically designed to benefit from this parameter difference.
Data Source
AI summary
A current reference circuit includes a native metal oxide semiconductor field effect transistor (MOSFET). The native MOSFET includes a source terminal coupled to ground. The current reference circuit also includes a transistor and an amplifier circuit. The transistor includes a first terminal coupled to a drain terminal of the native MOSFET, a second terminal coupled to a power supply rail, and a third terminal coupled to the drain terminal of the native MOSFET. The amplifier circuit includes an input terminal coupled to the drain terminal of the native MOSFET, and an output terminal coupled to a gate terminal of the native MOSFET.