Bandgap Reference Circuit for Low-Voltage Wide-Range Inputs
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Solution Overview
Problem
Bandgap voltage reference circuits face challenges in supporting lower input voltages and wider input ranges without increasing circuit complexity, often requiring operational amplifiers that enhance area and complexity.
Innovation Solution
A bandgap voltage reference circuit design incorporating a current mirror circuit, sub-circuits, and an output circuit using bipolar junction transistors and N-type transistors to generate currents independent of temperature, allowing for stable reference voltages without significant complexity increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If series connection of multiple resistors is used in bandgap voltage reference circuit, then voltage reference stability is improved, but voltage drop increases causing inability to support lower input voltages
Solution Approach 1:
The circuit segments the voltage reference generation into two independent paths: one path (through first resistor) generates current proportional to temperature, another path (through second resistor and N-type transistor) generates current compensating for temperature effects. This segmentation allows each path to be optimized independently, reducing total voltage drop while maintaining stability.
Solution Approach 2:
The invention changes the operating parameters by using bipolar junction transistors in forward active mode with specific base-emitter voltage relationships. By controlling the voltage across the first resistor to be approximately equal to the base-emitter voltage difference of the transistors, the circuit achieves temperature compensation with lower voltage headroom requirements.
2Adaptability or versatility
If operational amplifiers are added to solve voltage drop issue, then input voltage range is improved, but circuit area and complexity increase
Solution Approach 1:
The circuit uses self-service by employing the inherent exponential voltage-current characteristics of bipolar junction transistors to automatically generate temperature-compensated reference voltage. The transistor base-emitter voltages naturally provide the temperature compensation function without requiring external operational amplifiers or complex control circuits.
Solution Approach 2:
The invention uses a simplified copying approach where the current through the first resistor is mirrored and combined with the compensation current from the N-type transistor path. This current copying mechanism achieves the desired voltage reference function without replicating complex operational amplifier circuits.
3Reliability
If traditional bandgap circuit design is used, then voltage reference is generated, but power supply rejection ratio is insufficient
Solution Approach 1:
The circuit implements implicit feedback through the interconnected bipolar junction transistors and resistors. The base-emitter voltage relationships create a feedback mechanism that automatically adjusts the current distribution to maintain stable reference voltage despite power supply variations, improving power supply rejection ratio.
Solution Approach 2:
The invention uses a composite circuit structure combining bipolar junction transistors, resistors, and N-type transistors in a specific configuration. This composite structure leverages the complementary temperature coefficients of different components to achieve both high reliability and simplified design.
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
The design supports lower input voltages and wider input ranges while maintaining circuit simplicity and improving power supply rejection ratio (PSRR).
Implementation Method 1
The first sub-circuit is configured to generate a second current based on the second resistor and a base-emitter potential difference of the second bipolar junction transistor
Implementation Method 2
The first resistor is coupled between the emitter terminal of the first bipolar junction transistor and the ground source
Implementation Method 3
The first sub-circuit is configured to generate a second current based on the second resistor and a base-emitter potential difference of the second bipolar junction transistor
Implementation Method 4
The output circuit is configured to generate an output reference voltage based on the first current, the second current and the third resistor
Data Source
AI summary
A bandgap voltage reference circuit comprises a current mirror circuit, a first sub-circuit and an output circuit. The current mirror circuit is coupled between an input source and a ground, is configured to generate a first current, and comprises first and second bipolar junction transistors (BJTs) and a first resistor. The two BJTs' bases are coupled together. The first resistor is coupled between the first BJT's emitter and the ground. The first sub-circuit comprises a transistor coupled to the first BJT's base and collector, comprises a second resistor coupled between the transistor and the ground, and is configured to generate a second current based on the second resistor and a base-emitter potential difference of the second BJT. The output circuit is coupled between the input source and the ground, and is configured to generate an output reference voltage based on the first, second currents and a third resistor.