Voltage Reference Circuit Beta Compensation
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Solution Overview
Problem
Existing voltage reference circuits in electronic systems face challenges in achieving high precision over temperature variations, with typical bandgap references offering only about one percent accuracy, which is insufficient for certain applications, and are further complicated by process dependencies and inaccuracies in modern semiconductor processes.
Innovation Solution
A voltage reference circuit utilizing two bipolar-junction transistors with different emitter sizes and resistor ratios, along with real-time measurement and trimming of resistors R2 and R3, to compensate for temperature and process variations, specifically addressing the curvature and offset caused by beta ratios, thereby achieving a voltage reference with minimal variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional bandgap reference circuit is used, then the circuit provides a voltage reference with about one percent voltage variation over temperature, but the precision is insufficient for systems requiring better than one percent accuracy
Solution Approach 1:
The patent changes the parameters of the bandgap reference circuit by introducing beta-sensing transistors and additional feedback paths that dynamically adjust the reference voltage based on measured beta values. This allows the circuit to compensate for process variations and achieve better than one percent precision while maintaining temperature stability.
Solution Approach 2:
The patent implements feedback mechanisms where the measured beta ratio is used to adjust the reference voltage through trim circuits. The feedback loop continuously monitors and corrects for deviations caused by process variations, enabling the circuit to achieve high precision without sacrificing temperature reliability.
2Manufacturing precision
If resistor trimming is performed to adjust for process variations, then manufacturing precision is improved, but the device complexity increases due to additional trimming circuits
Solution Approach 1:
The patent employs self-service principles by using the circuit's own operation to generate the trimming information. The beta-sensing transistors automatically measure the beta ratio during normal operation, and the trim circuits use this information to self-adjust the reference voltage without requiring external calibration equipment or complex manufacturing processes.
Solution Approach 2:
The patent performs preliminary action by pre-configuring the beta-sensing transistors and trim circuits to automatically compensate for process variations before the circuit is put into service. The trimming is done in advance based on measured beta values, eliminating the need for complex post-manufacturing adjustments.
3Measurement precision
If beta ratio variations are compensated for, then voltage reference accuracy is improved, but the device complexity increases due to additional transistors and measurement circuits
Solution Approach 1:
The patent applies universality by designing the beta-sensing transistors to serve multiple functions: they act as both the primary reference elements and the sensing elements for beta measurement. This multi-functionality allows the circuit to achieve high accuracy through beta compensation without requiring separate dedicated sensing components, thereby limiting the increase in device complexity.
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 achieves a voltage reference with approximately 0.2% variation over a significant temperature range, effectively addressing the limitations of traditional bandgap references by compensating for process and temperature-related inaccuracies.
Implementation Method 1
a first voltage source that has a positive temperature coefficient (voltage increases with temperature) is summed with a second voltage source that has a negative temperature coefficient and the two temperature dependencies cancel
Data Source
AI summary
A voltage reference circuit includes a bipolar transistor and a circuit configured to measure the ratio of emitter current to base current of the bipolar transistor. The output voltage of the voltage reference circuit is compensated as a function of the measured ratio.