Bandgap Reference Circuit Isolation for Noise-Immune Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bandgap reference circuits in mixed signal integrated circuits face challenges in providing a precise reference voltage that remains stable against temperature and load variations, particularly due to noise and substrate injection issues.
Innovation Solution
The proposed bandgap circuit design utilizes two bipolar junction transistors with their collectors isolated from the bandgap core, incorporating resistor networks and an error amplifier to generate a noise-immune reference voltage, with a trim resistor for temperature compensation, ensuring the bandgap voltage remains constant across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If collectors of BJTs are coupled to the bandgap core circuit, then current control is simplified, but noise and substrate injection affect the reference voltage
Solution Approach 1:
The patent extracts the collectors of the bipolar junction transistors from the bandgap core circuit, isolating them to prevent noise and substrate injection from affecting the reference voltage. This separation removes the harmful coupling between the collector nodes and the sensitive bandgap core, thereby improving noise immunity while maintaining the essential current control functions through alternative pathways.
2Stability of the object's composition
If a complex resistor network and error amplifier are used, then temperature stability is improved, but circuit complexity increases
Solution Approach 1:
The patent employs an error amplifier that provides feedback to maintain temperature stability. The error amplifier compares the actual output voltage with the desired reference voltage and adjusts the operating point of the bipolar junction transistors accordingly, compensating for temperature variations and ensuring stable reference voltage output despite environmental changes.
3Measurement precision
If collectors are isolated from the bandgap core, then noise impact is reduced, but current distribution control becomes more difficult
Solution Approach 1:
The patent introduces intermediate coupling elements, specifically resistors and the error amplifier, that mediate between the isolated collectors and the bandgap core circuit. These intermediaries allow precise control of current distribution to the transistors without directly coupling the collectors to the sensitive core, thereby maintaining both noise isolation and current control capability.
Data Source
AI summary
In a described example, a circuit includes a first bipolar junction transistor (BJT) having a first base, a first emitter and a first collector. A second BJT has a second base, a second emitter and a second collector, in which the first collector is coupled to the second collector. A bandgap core circuit has first and second core inputs and a bandgap output. The first core input is coupled to the first emitter, the second core input is coupled to the second emitter, and the first and second bases are coupled to the bandgap output.