Constant-Current Circuit Using Opposite Tempco Resistors
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Solution Overview
Problem
Existing circuits for generating bias or reference currents suffer from variability in output current due to temperature and process fluctuations, affecting the performance of systems like RF amplifiers and sensors.
Innovation Solution
A circuit assembly using a resistor pair with one resistor having a positive temperature coefficient and another with a negative temperature coefficient, configured to cancel out temperature variations, combined with a trimming component to compensate for process variations, generates a current with a zero temperature coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single resistor is used to generate reference current, then the circuit is simple, but the output current varies with temperature
Solution Approach 1:
The single resistor is segmented into two separate resistors with different temperature coefficients (positive and negative). By dividing the resistance function into two independent components, each with complementary temperature characteristics, the overall current stability is improved while maintaining relatively simple circuit structure.
Solution Approach 2:
The patent uses a composite approach by combining two resistors with opposite temperature coefficients (one with positive temperature coefficient and one with negative temperature coefficient). This composite resistor configuration compensates for temperature variations, achieving stable current output across temperature ranges.
2Measurement precision
If additional trimming components are added to compensate for process variation, then current precision improves, but device complexity increases
Solution Approach 1:
The resistor pair with opposite temperature coefficients serves its own trimming function. The inherent temperature compensation特性 of the paired resistors automatically compensates for process variations without requiring external trimming components or additional adjustment mechanisms, thus improving current precision while avoiding increased device complexity.
3Reliability
If off-die components are used for temperature compensation, then current stability improves, but the need for additional components increases device complexity
Solution Approach 1:
The temperature compensation function is merged with the existing resistor structure by using two resistors with opposite temperature coefficients that are already part of the current generation circuit. This eliminates the need for separate off-die compensation components, achieving current stability while keeping the device complexity low.
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 solution provides a stable current output that reduces variability over temperature and process, improving the performance of RF amplifiers and sensors by maintaining consistent bias or reference currents.
Implementation Method 1
the first and second resistors being configured such that a variability of resistance over temperature of the first resistor and a variability of resistance over temperature of the second resistor cancel to produce a zero temperature coefficient for the resistor pair
Data Source
AI summary
A circuit assembly for generating a constant current, the circuit comprising: a resistor pair including a first resistor and a second resistor, the first resistor having a positive temperature coefficient and the second resistor having a negative temperature coefficient, the first and second resistors being configured such that the variability of resistance over temperature of the first resistor and the variability of resistance over temperature of the second resistor cancel to produce a zero temperature coefficient for the resistor pair; and a voltage input connected to the resistor pair and configured to receive an input voltage, the voltage input and the resistor pair configured to generate a current with a zero temperature coefficient.