Bandgap Reference Circuit Using Input Amplifier for Low-Frequency Noise
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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 inherent noise generation from bipolar junction transistors and operational amplifier input pairs.
Innovation Solution
Incorporating a gain stage within the bandgap network, utilizing a combination of bipolar junction transistors and resistors, and configuring the operational amplifier to attenuate flicker noise through specific transistor sizing and resistor arrangements, effectively reducing low-frequency noise without significant power expenditure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional bandgap reference circuits are used, then reference voltage is provided, but low-frequency flicker noise is generated from bipolar junction transistors and operational amplifier input pairs
Solution Approach 1:
The patent extracts and removes the harmful flicker noise component from the bandgap reference circuit by carefully selecting and sizing the operational amplifier input transistors to minimize noise generation, while maintaining the essential reference voltage function
Solution Approach 2:
The patent changes the parameters of the operational amplifier input transistors, specifically the width-to-length ratio (W/L), to optimize the balance between noise reduction and power consumption. By adjusting these transistor dimensions, the flicker noise is attenuated without significantly increasing power expenditure
2Object-affected harmful factors
If techniques are used to eliminate low-frequency noise, then noise reduction is achieved, but excessive power consumption occurs
Solution Approach 1:
The patent optimizes transistor sizing parameters to achieve noise reduction with minimal power penalty. Specifically, the input transistors of the operational amplifier are sized to provide noise attenuation while maintaining efficient power consumption suitable for low-power applications
Solution Approach 2:
The patent applies partial action by implementing noise reduction only where most needed (at the operational amplifier input stage) rather than throughout the entire circuit, thereby achieving effective flicker noise attenuation without excessive power consumption across all circuit components
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.