Temperature-Compensated Current Source Circuit Using Mirroring Transistors
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Solution Overview
Problem
Current current source circuits in semiconductor electronics are sensitive to temperature changes, affecting the stability and performance of semiconductor circuits due to varying characteristics of passive and active elements with temperature, leading to instability in reference bias circuits.
Innovation Solution
A current generating circuit comprising a first current source with a negative temperature coefficient, a second current source with a positive temperature coefficient, and a compensation circuit using mirroring transistor structures to generate a constant current with a reduced temperature coefficient, allowing for stable operation across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional current source circuit is used, then the circuit can provide reference bias current, but the current becomes sensitive to temperature changes causing instability
Solution Approach 1:
The current source circuit is divided into multiple parallel branches, each containing transistors with different temperature coefficients. One branch contains transistors exhibiting negative temperature coefficient characteristics while another branch contains transistors exhibiting positive temperature coefficient characteristics, allowing independent optimization of each segment's temperature response
Solution Approach 2:
The invention changes the temperature coefficient parameter of different transistor branches to compensate for temperature variations. By selecting transistors with opposite temperature coefficient signs and adjusting their respective current contributions, the overall circuit achieves temperature-independent operation where the sum of currents remains constant across temperature changes
2Reliability
If temperature compensation is implemented using multiple current sources with different temperature coefficients, then temperature stability is improved, but circuit complexity increases
Solution Approach 1:
Multiple current-generating branches are merged into a single parallel configuration sharing common connection nodes. The branches are combined such that their current contributions sum together to form the total output current, reducing the need for separate compensation circuits while achieving temperature stability through the inherent properties of the parallel structure
Solution Approach 2:
The transistor branches serve dual functions: they generate reference currents for biasing while simultaneously providing temperature compensation. The same transistors that establish the operating points also contribute to temperature stabilization, eliminating the need for dedicated compensation components and reducing overall circuit complexity
Data Source
AI summary
A current generating circuit that includes a first current source that generates a first current having a negative temperature coefficient a second current source that generates a second current having a positive temperature coefficient. A compensation circuit generates a common current using a first transistor that receives the first current and a second transistor formed in a mirroring structure, a third transistor that receives the second current, and a fourth transistor formed in a mirroring structure. In addition, the compensation circuit provides the common current as an output current using a transistor that is formed in at least a pair of mirroring structures.