Bandgap Reference Circuit with Gain Stage for Flicker Noise Reduction
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Solution Overview
Problem
Bandgap reference voltage supplies face challenges in reducing low-frequency flicker noise without excessive power consumption, which is particularly difficult in low-power applications due to the limitations of using large filter capacitors.
Innovation Solution
Incorporating a gain stage within the bandgap network, utilizing a configuration of bipolar junction transistors (BJTs) and resistors, and optimizing the operational amplifier's input pair to attenuate flicker noise through a combination of PTAT and CTAT voltage sources, while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If large filter capacitors are used to reduce low-frequency flicker noise, then noise reduction is improved, but power consumption increases and device area increases
Solution Approach 1:
The patent extracts and addresses the noise problem at its source by modifying the operational amplifier's input stage and adding a gain stage within the bandgap network, rather than using large filter capacitors to filter the noise after it is generated. This approach reduces low-frequency flicker noise without requiring large external filtering components that consume power and occupy area.
Solution Approach 2:
The patent introduces a gain stage as an intermediary element within the bandgap reference network. This gain stage amplifies the signal before it reaches the operational amplifier, effectively reducing the impact of flicker noise without requiring additional filtering components. The gain stage acts as a mediator that improves noise performance while maintaining low power consumption.
2Object-affected harmful factors
If large filter capacitors are used to reduce low-frequency flicker noise, then noise reduction is improved, but device area increases
Solution Approach 1:
The patent removes the need for large external filter capacitors by addressing the noise problem internally through circuit design modifications. The gain stage and modified input stage eliminate flicker noise at its source, freeing up device area that would otherwise be occupied by large filtering components.
Solution Approach 2:
The patent changes the electrical parameters of the bandgap reference circuit by adding a gain stage and modifying the input stage configuration. These parameter changes improve the noise performance without requiring physical filtering components, thereby reducing the overall device area while maintaining effective noise reduction.
3Object-affected harmful factors
If the operational amplifier's input pair is optimized to reduce flicker noise, then noise reduction is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the gain stage with the bandgap reference network, combining multiple functions into a single integrated structure. The gain stage is implemented using the existing BJTs and resistors in the bandgap network, eliminating the need for separate noise reduction circuits and reducing overall complexity while effectively reducing flicker noise.
Solution Approach 2:
The operational amplifier's input pair is designed to serve multiple functions: it provides the necessary amplification for the bandgap reference while simultaneously reducing flicker noise through its optimized configuration. This multi-functionality reduces the need for additional dedicated noise reduction components, thereby limiting the increase in circuit complexity.
Data Source
AI summary
A bandgap reference circuit includes first through fourth bipolar junction transistors (BJTs). The base and collector of the first BJT are shorted together. The second BJT is coupled to the first BJT via a first resistor. The base of the third BJT is coupled to the base of the first BJT. The base and collector of the fourth BJT are coupled together and also are coupled to the base of the second BJT. A second resistor is coupled to the fourth emitter of the fourth BJT. A third resistor is coupled to the second resistor and to the emitter of the second BJT. An operational amplifier has a first input coupled to the first resistor and the collector of the second BJT, a second input coupled to the emitter of the third BJT and the collector of the fourth BJT, and an output coupled to the collectors of the first and third BJTs.