Weak Inversion Transistor Reference Current Circuit
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Solution Overview
Problem
Existing analog and hybrid circuits require low and very low reference currents, but highly stable reference current circuits are expensive and not efficiently addressed by current technologies.
Innovation Solution
A system comprising multiple transistors in weak inversion state, connected to a low current source and voltage supply, with a multiplication and subtraction circuit that adjusts the current based on a current reduction variable and voltage reduction signal to provide a stable low reference current, proportional to the pixel output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If highly stable reference current circuits are used, then current stability is improved, but circuit cost increases
Solution Approach 1:
The patent changes the operating parameters of transistors by utilizing weak inversion mode instead of strong inversion mode, allowing the circuit to achieve stable reference current at lower costs. The invention modifies the transistor operation state parameter to enable cost-effective generation of very low reference currents while maintaining stability.
2Device complexity
If conventional transistor configurations are used, then circuit simplicity is maintained, but current precision deteriorates
Solution Approach 1:
The patent implements feedback mechanisms through the amplifier circuit that monitors and adjusts the transistor gate voltages to maintain precise current ratios. The feedback loop ensures that the reference current remains stable and precise while using relatively simple transistor configurations.
Solution Approach 2:
The patent replaces complex mechanical adjustment mechanisms with electronic feedback control using amplifiers and voltage sources. This substitution allows for more precise current control without increasing physical circuit complexity, achieving high current precision through electronic rather than mechanical means.
3Power
If multiple transistors in parallel are used, then current magnitude is improved, but current control precision deteriorates
Solution Approach 1:
The patent segments the current control into separate parallel transistor branches, each controlled by independent voltage sources. This segmentation allows the circuit to achieve high current magnitude through parallel operation while maintaining precision through independent control of each branch, preventing current imbalance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively provides a stable low reference current, reducing costs by utilizing a network of transistors and amplifiers to adjust current levels, ensuring efficient operation in circuits such as camera pixels.
Implementation Method 1
multiple transistors that include a first transistor that is maintained in a weak inversion state
Data Source
AI summary
A system that includes: multiple transistors that comprise a first transistor that is maintained in a weak inversion state; wherein sources of the multiple transistors are coupled to a low current source; wherein drains of the multiple transistors are coupled to a voltage supply source; a first amplifier that has a positive input, negative input and an output; wherein the positive input receives an input voltage; wherein the negative input is coupled to a source of the first transistor; wherein the output is coupled to a gate of the first transistor and to a multiplication and subtracting circuit; a multiplication and subtraction circuit that is coupled to the first amplifier and outputs an output signal that equals a difference between the input voltage and a product of a current reduction variable and a voltage reduction signal; wherein the voltage reduction signal is associated with a current reduction factor; wherein the output signal is provided to a second transistor that is maintained in weak inversion; and wherein the second transistor outputs, in response to a reception of the output signal, a current that is responsive to the pixel output signal, is proportional to the low current and is inversely proportional to the current reduction variable and the current reduction factor.