Bandgap Reference Trimming for Low-Voltage Temperature Stability
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Solution Overview
Problem
Conventional bandgap reference circuits face challenges in generating accurate reference currents and voltages due to the large number of circuit components, which contribute to errors, size, cost, and complexity, especially in maintaining temperature independence and accuracy over a range of temperatures.
Innovation Solution
A low supply voltage BiCMOS self-biased bandgap reference circuit with a trimming circuit that adjusts the base current of bipolar transistors to generate a bandgap reference voltage and current with zero temperature coefficient, using a combination of PTAT and CTAT currents and a trimming circuit to compensate for base current contributions, thereby reducing curvature over temperature and process variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional bandgap reference circuits use multiple bipolar transistors and circuit components to generate accurate reference currents, then the accuracy and temperature independence are improved, but the device complexity, size, and cost increase
Solution Approach 1:
The patent extracts and eliminates unnecessary circuit components from conventional bandgap reference designs. By removing redundant transistors and simplifying the circuit topology while retaining the essential PTAT and CTAT current generation mechanisms, the invention achieves accurate reference current output with reduced device complexity and lower component count
Solution Approach 2:
The patent merges multiple circuit functions into fewer integrated components. The simplified circuit architecture combines the temperature compensation mechanism and reference current generation into a more compact configuration, reducing the overall number of discrete components while maintaining the temperature-independent reference current characteristic
2Power
If conventional bandgap reference circuits use large numbers of circuit components including bipolar transistors, then the reference voltage can be generated, but errors and curvature over temperature increase
Solution Approach 1:
The patent converts the inherently temperature-dependent behavior of bipolar transistors into a benefit by precisely controlling and compensating for their base current contributions. By using a reduced number of carefully selected bipolar transistors with optimized sizing ratios, the circuit transforms potential error sources into controlled elements that maintain temperature stability
Solution Approach 2:
The patent optimizes critical circuit parameters including transistor sizing ratios and current scaling factors to minimize temperature-induced curvature in the reference output. By carefully adjusting these parameters and using precise resistor ratios, the circuit achieves reduced temperature coefficients and improved reliability across varying temperature conditions
3Stability of the object's composition
If conventional bandgap reference circuits combine PTAT and CTAT currents through multiple circuits, then a temperature-independent reference current is formed, but the number of circuit components and base current errors increase
Solution Approach 1:
The patent segments the temperature compensation function into distinct PTAT and CTAT current paths that can be independently optimized and then combined. By separating these functions into dedicated current mirrors and generation circuits with minimal overlapping components, the invention achieves temperature independence while minimizing the total component count and reducing interaction-induced errors
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 improved accuracy and temperature independence for bandgap reference circuits, reducing the need for extra circuitry and enabling low voltage operation, with a curvature of the bandgap reference voltage reduced to 0.7 mV or less over temperature, enhancing the robustness and accuracy of the generated reference currents and voltages.
Implementation Method 1
first and second bipolar transistors having different sizing reference values for generating a first current at a first resistor, wherein the first current varies proportionally as a function of temperature
Implementation Method 2
a third current generator configured to generate a third current based on a base current of the third bipolar transistor; and a trim control circuit configured to modify the second current by adding the third current to the second current or subtracting the third current from the second current
Implementation Method 3
using a combination of PTAT and CTAT currents and a trimming circuit to compensate for base current contributions, thereby reducing curvature over temperature and process variations
Data Source
AI summary
A bandgap reference circuit includes a first current generator having first and second bipolar transistors for generating a first current that varies proportionally as a function of temperature. A second current generator includes a field effect transistor for generating a second current that varies inversely as a function of temperature. A trimming circuit includes a third bipolar transistor sized to match the first bipolar transistor, a third current generator having a second field effect transistor coupled to a collector and base of the third bipolar transistor to generate a third current based on a base current of the third bipolar transistor, and a trim control circuit configured to modify the second current by adding the third current to or subtracting the third current from the second current based on a trim control signal. A bandgap reference current is generated by summing the first current and the modified second current.