Bandgap Reference Regulator Circuit for Low-Noise Stable Output
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Solution Overview
Problem
Conventional bandgap circuitry becomes unstable when significant current is drawn from its output node, making it unsuitable for supplying reference voltage signals to current-drawing external circuitry, and suffers from noise and interference issues due to operational amplifiers contributing thermal noise and flicker noise, as well as cross-talk between multiple LDO output stages.
Innovation Solution
The signal-generation circuitry incorporates a differential amplifier with shared components between the bandgap voltage reference circuitry and regulation stage, utilizing current-mirror transistors and shared resistors to reduce noise and stabilize the voltage reference signal, while a bandgap reference circuit generates a temperature-independent voltage signal by summing opposing temperature coefficients, and a capacitor filters noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional bandgap circuitry is connected to a resistive load, then current can be drawn from the output node, but the bandgap circuit becomes unstable and malfunctions
Solution Approach 1:
The circuit is divided into two functional segments: a bandgap reference circuit that generates the stable voltage and an LDO output stage that handles the current delivery to the load. This segmentation allows the bandgap circuit to remain stable while the LDO stage absorbs the current drawing requirements.
Solution Approach 2:
The LDO output stage acts as an intermediary between the bandgap reference circuit and the external load. It buffers the bandgap output, allowing current to be drawn without directly loading the sensitive bandgap node, thus maintaining stability while enabling current delivery.
2Reliability
If operational amplifier is used in LDO output stage, then voltage regulation is achieved, but thermal noise and flicker noise are introduced
Solution Approach 1:
The bandgap reference circuit and LDO output stage are merged into a single integrated circuit block. This merging allows the noise generated by the operational amplifier to be correlated with and cancel against noise from the bandgap reference, reducing overall output noise while maintaining voltage regulation functionality.
3Device complexity
If multiple LDO output stages share the same bandgap reference, then cross-talk occurs between instances, but component sharing reduces complexity
Solution Approach 1:
Each LDO output stage is given its own dedicated bandgap reference circuit instance. This segmentation eliminates cross-talk between multiple LDO stages by providing isolated reference sources, at the cost of increased overall circuit complexity and component count.
4Reliability
If bandgap circuitry is designed for temperature independence, then reference voltage stability is achieved, but the output voltage is difficult to increase above a certain value
Solution Approach 1:
The LDO output stage serves as an intermediary that takes the fixed bandgap reference voltage and regulates it to a higher output voltage level. This allows the temperature-stable reference to be transformed into a versatile output that can be increased above the original bandgap voltage level while maintaining stability.
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
This approach enhances noise performance, stabilizes voltage reference signals, and eliminates cross-talk between multiple instances, providing a low-noise, temperature-independent voltage-regulated signal that can be used in phase locked loop and digital-to-analogue converter circuitry.
Implementation Method 1
The capacitor 148 is connected between the bandgap-regulator circuitry output node 150 and the ground voltage supply 170 and is configured to filter high frequency noise from the regulated-reference voltage signal
Implementation Method 2
a bandgap reference circuit generates a temperature-independent voltage signal by summing opposing temperature coefficients
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Signal-generation circuitry comprising: a differential amplifier comprising first and second input transistors connected along first and second corresponding current paths, control terminals of the first and second input transistors serving as corresponding first and second input terminals of the differential amplifier, the differential amplifier having an output terminal at which an amplified signal is output dependent on first and second input signals received at the first and second input terminals, respectively; bandgap voltage reference circuitry also comprising said first current path having said first input transistor, the bandgap voltage reference circuitry further comprising a third current path having a third input transistor, wherein the control terminals of the first and third input transistors are connected together to form a reference terminal at which a bandgap voltage reference signal is generated as said first input signal; and a regulation stage connected to receive the amplified signal output from the differential amplifier and configured to generate a voltage-regulated signal based thereon, and connected to the second input terminal of the differential amplifier so that the second input signal is a feedback signal dependent on the voltage-regulated signal.