Sample-and-Hold Bandgap Circuit for Low-Power Stable Reference
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Solution Overview
Problem
Bandgap circuits used in battery-powered applications face challenges with high power consumption and large layout area due to high resistances, which also result in significant noise levels.
Innovation Solution
A bandgap circuit design incorporating a voltage generator circuit with a pair of transistors in diode configuration and a sample and hold circuit, which samples and buffers voltages to generate a stable output, reducing the need for high resistances and minimizing layout area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high resistances are used in the voltage generator circuit to reduce current consumption, then power consumption is reduced, but layout area increases and noise increases
Solution Approach 1:
The patent implements periodic sampling of voltages across the transistors using a sample-and-hold circuit that operates in discrete phases. During the sample phase, voltages are captured; during the hold phase, the sampled values are maintained and used to generate the output. This periodic operation allows the use of lower resistances without increasing continuous power consumption, as the current-drawing elements are active only during sampling intervals.
Solution Approach 2:
The patent introduces a sample-and-hold circuit as an intermediary between the voltage generator circuit and the output. This intermediary captures voltage samples during brief intervals and holds them for output generation, eliminating the need for high-value resistors that would otherwise be required to limit continuous current flow. The intermediary enables decoupling of voltage generation from continuous current consumption.
2Use of energy by moving object
If high resistances are used in the voltage generator circuit to reduce current consumption, then power consumption is reduced, but noise level increases
Solution Approach 1:
The periodic sampling operation limits the duration during which resistive elements are active, thereby reducing the integrated noise contribution. By confining current flow to brief sampling intervals rather than continuous operation, the white noise generated by resistors is significantly reduced while maintaining acceptable power consumption levels.
Solution Approach 2:
The sample-and-hold circuit acts as a noise-filtering intermediary by capturing voltage information during brief intervals and holding it for subsequent use. This intermediary approach avoids the need for high-value resistors that would generate excessive thermal noise, as the voltage sampling occurs during controlled, limited-time windows.
3Stability of the object's composition
If the voltage generator circuit operates continuously to provide stable output, then output stability is improved, but power consumption increases
Solution Approach 1:
The patent employs periodic sampling with a sample-and-hold circuit that captures voltage values during brief intervals and maintains them during hold phases. This periodic operation provides stable output during the hold phase while consuming power only during sampling intervals, thereby achieving a balance between output stability and power consumption that continuous operation cannot provide.
Solution Approach 2:
The voltage values are sampled and held in advance before being used to generate the output. This preliminary action allows the output to be generated from pre-captured voltage samples during the hold phase, eliminating the need for continuous voltage generation and reducing power consumption while maintaining output stability.
Data Source
AI summary
A bandgap circuit that is area efficient and has a low power consumption. The bandgap circuit includes a voltage generator circuit, and a sample and hold circuit coupled to the voltage generator circuit. The voltage generator circuit includes a pair of transistors each connected in a diode configuration and biased with a respective current source of a plurality of current sources of the voltage generator circuit. During a sample phase, the sample and hold circuit samples a first voltage between a first base and a first emitter of a first transistor of the pair of transistors and a second voltage between a second base and a second emitter of a second transistor of the pair of transistors. During a hold phase subsequent to the sample phase, the sample and hold circuit generates an output voltage as a combination of the sampled first and second voltages.