Bias Current Generator Leakage Control Circuit
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Solution Overview
Problem
Bias current generator circuits face accuracy issues due to high reverse leakage currents from reverse-biased junction diodes, especially under high temperature conditions, which affect the bias current and deteriorate the performance, especially in ultra-low power applications.
Innovation Solution
Incorporating a leakage control circuit that includes a series connection of transistors to manage the reverse leakage current by applying a driving voltage to the well contact of the diffusion resistor, allowing the leakage current to flow into the leakage control circuit and minimizing its impact on the bias current path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the well contact of the diffusion resistor is connected to the supply voltage, then the reverse leakage current flows into the second current path, but this deteriorates the accuracy of the bias current generator circuit
Solution Approach 1:
The patent divides the current paths by introducing a third current path that is isolated from the first and second current paths. The diffusion resistor is moved to the third current path, which is connected to the supply voltage through a separate transistor. This segmentation prevents the reverse leakage current from affecting the bias current generator circuit while maintaining proper circuit operation.
Solution Approach 2:
The patent introduces a third current path as an intermediary between the supply voltage and the diffusion resistor. This intermediate path, controlled by a third transistor, acts as a mediator that allows the diffusion resistor to be properly biased while isolating its reverse leakage current from the sensitive bias current generator circuit.
2Measurement precision
If the well contact of the diffusion resistor is not connected to supply voltage, then reverse leakage current is reduced, but the diffusion resistor cannot be properly biased
Solution Approach 1:
The patent segments the biasing function from the measurement function by creating a separate third current path. The diffusion resistor receives its bias voltage through this isolated path, ensuring proper operation without introducing leakage current into the sensitive bias current generator circuit.
Solution Approach 2:
The third current path serves as an intermediary that provides the necessary bias voltage to the diffusion resistor while preventing the reverse leakage current from contaminating the bias current generator circuit. This intermediate structure resolves the conflict between proper biasing and leakage reduction.
3Measurement precision
If a third current path is introduced to isolate the diffusion resistor, then reverse leakage current is prevented from affecting the bias current, but the circuit complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the circuit into three distinct current paths, each with a specific function. While this increases the number of components, it provides a clean and systematic solution that clearly separates the biasing function from the measurement function, making the circuit easier to analyze and maintain despite the increased complexity.
Solution Approach 2:
The third transistor and third current path serve multiple functions: they provide bias voltage to the diffusion resistor, isolate the reverse leakage current from the sensitive circuits, and maintain proper operation of the bias current generator. This multi-functionality justifies the additional components by consolidating several requirements into a single integrated solution.
Data Source
AI summary
A bias current generator circuit includes a current path and a leakage control circuit. The current path is connected between a supply voltage and a ground level. The current path includes a transistor and a resistor. The transistor has a current channel connected in the current path. The resistor has an upper terminal and a lower terminal connected in the current path, and a well contact to allow a reverse leakage current of the resistor to flow through. The leakage control circuit is connected to the supply voltage. The leakage control circuit includes a driving transistor to provide a driving voltage to the well contact of the resistor, and to allow the reverse leakage current of the resistor to flow into the leakage control circuit.