Stacked Delta VBE Generator for Low Noise Bandgap Reference
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Solution Overview
Problem
Conventional bandgap voltage reference circuits require a large number of transistors and higher input voltages to achieve a high ΔVBE, leading to increased noise and cost, while also being inefficient in die area usage.
Innovation Solution
The proposed solution involves stacking multiple ΔVBE generators in a Dobkin cell configuration without increasing the input voltage, using identical stages to achieve a larger ΔVBE with fewer transistors and reduced noise, and employing additional techniques such as resistor modifications and VBE multipliers to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional bandgap voltage reference circuits use a large number of transistors to achieve high ΔVBE, then the ΔVBE value is improved, but the noise increases and die area consumption increases
Solution Approach 1:
The patent divides the ΔVBE generation function into multiple independent stages, where each stage contributes a portion of the total ΔVBE. This segmentation allows the circuit to achieve high overall ΔVBE without requiring an excessively large number of transistors in a single stage, thereby reducing noise while maintaining precision.
Solution Approach 2:
The patent transitions from a single-stage ΔVBE generation approach to a multi-stage cascaded architecture, adding a dimensional aspect to the circuit design. This dimensional change enables the system to achieve high ΔVBE through cumulative effect of multiple stages rather than relying on a single high-ratio transistor pair, thus reducing noise and die area.
2Measurement precision
If conventional bandgap voltage reference circuits use a large number of transistors to achieve high ΔVBE, then the ΔVBE value is improved, but the die area consumption increases
Solution Approach 1:
The patent segments the ΔVBE generation into multiple functional stages, each implemented with a compact transistor pair. This segmentation allows efficient use of die area by distributing the functionality across modular units rather than requiring a single large transistor pair, thus achieving high ΔVBE with reduced overall die area consumption.
Solution Approach 2:
The patent employs universal building blocks that can be replicated and cascaded to achieve the desired ΔVBE. Each stage uses a standardized transistor pair configuration that performs multiple functions (ΔVBE generation, current mirroring, etc.), improving die area efficiency through functional integration and reuse of circuit motifs.
3Measurement precision
If conventional bandgap voltage reference circuits increase the number of transistors, then the ΔVBE value is improved, but the circuit complexity increases
Solution Approach 1:
The patent divides the complex ΔVBE generation task into multiple simpler stages, where each stage is relatively simple but collectively they achieve the high ΔVBE value. This segmentation reduces the complexity of individual circuit blocks while maintaining the overall precision through cascaded architecture.
Solution Approach 2:
The patent combines multiple identical or similar circuit stages in a cascaded manner to achieve high ΔVBE. By merging the functionality of multiple simple stages rather than using a single complex stage, the overall circuit complexity is managed more effectively while achieving the desired precision.
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
This approach allows for a significant reduction in the number of transistors required, maintains low noise levels, and avoids the need for higher input voltages, achieving a larger ΔVBE with less die area and improved performance.
Implementation Method 1
Bandgap voltage references are generally produced by summing a Proportional To Absolute Temperature (PTAT) voltage and a Complementary To Absolute Temperature (CTAT) voltage together to generate a temperature independent voltage. A CTAT voltage can be produced using a diode or diode connected Bipolar Junction Transistor (BJT).
Implementation Method 2
The PTAT voltage can be produced by developing a voltage across a resistor with a PTAT current. A ΔVBE circuit may be employed to generate a PTAT current using two BJTs with different current densities. The PTAT current used is usually proportional to the logarithm of the current density ratio of the two BJTs and can be mathematically described as IPTAT=ΔVBE/R=(VT/R)*ln(J1/J2).
Data Source
AI summary
Method and system for developing low noise bandgap references. A stacked ΔVBE generator is disclosed for generating ΔVBE. The stacked ΔVBE generator includes an error amplifier configured to generate an output based on an error signal provided by a first stack of the ΔVBE generator. The first stack of the ΔVBE is coupled to a first sub-circuit and the error amplifier to form a closed loop. The first sub-circuit is coupled to a power supply and ground and configured to provide a source current between the power supply and the ground. The stacked ΔVBE generator also includes a second sub-circuit coupled to the output of the error amplifier, the first and second stacks, and the ground, as well as a second stack of the ΔVBE generator, which is coupled to the first stack and the second sub-circuit. The ΔVBE is measured at outputs of the first and second stacks and equals the sum of individual ΔVBEs of the first and second stacks.