Temperature Stable Reference Current Circuit Design
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Solution Overview
Problem
Existing reference current generation circuits in biasing circuits experience fluctuations due to temperature changes, leading to increased power consumption and decreased battery life in portable electronics, as well as performance degradation in analog circuits.
Innovation Solution
A system comprising multiple current generators and mirrors that generate and mirror currents in inverse response to temperature changes, ensuring a substantially constant reference current by summing the mirrored currents, thereby maintaining stability across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If conventional reference current generation circuits are used, then circuit operation is enabled, but reference current fluctuates with temperature changes leading to increased power consumption
Solution Approach 1:
The patent changes the operating parameters of MOSFETs by utilizing the inverse temperature dependence between saturation current (increases with temperature) and mobility (decreases with temperature). By carefully designing the circuit to exploit these opposing parameter changes, the reference current remains stable across temperature variations, preventing power consumption increases.
Solution Approach 2:
The circuit implements implicit feedback through the interconnected MOSFET configuration where temperature-induced changes in one transistor's current are compensated by opposite changes in another transistor's mobility characteristics. This self-regulating mechanism maintains constant reference current without external temperature sensing or active control.
2Duration of action of stationary object
If reference current increases with temperature, then circuit operation continues, but battery life decreases in portable electronics
Solution Approach 1:
The patent exploits the temperature parameter changes in MOSFET characteristics - specifically that saturation current increases with temperature while mobility decreases. The circuit is designed so these opposing parameter changes cancel each other out, maintaining stable reference current and thus stable power consumption, which extends battery life in portable applications.
3Reliability
If reference current fluctuates with temperature, then circuit remains simple, but analog circuit performance degrades
Solution Approach 1:
The patent maintains analog circuit performance by exploiting parameter changes in MOSFETs - the inverse temperature dependence between saturation current and mobility. The circuit uses standard MOSFET operations in saturation mode without requiring complex temperature compensation networks, trimming circuits, or calibration mechanisms, thus maintaining simplicity while ensuring reliable analog performance.
Data Source
AI summary
A circuit for generating a constant current includes a first current generator that conducts a first current based upon a supply voltage and a resistive element and that generates a first mirrored current based on the current, a second current generator that generates a second current based on the first current wherein the second mirrored current decreases as the current increases and decreases as the current increases and a summing circuit for summing currents proportional to said first and second currents to generate an output current.