Bandgap Voltage Reference Circuit Noise Reduction
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Solution Overview
Problem
Bandgap voltage reference circuits face significant low-frequency noise due to bipolar transistors, which is difficult to mitigate without increasing current consumption, transistor size, or design complexity, and this noise dominates at low frequencies, affecting power efficiency and integrated circuit performance.
Innovation Solution
The implementation of a bandgap voltage reference circuit design that includes specific resistor configurations and transistor arrangements to minimize noise contributions from bipolar transistors, particularly by setting the resistance of base resistors according to the reciprocal of transconductance and using a ΔVbe/R circuit portion with different emitter areas for transistors, effectively canceling noise voltage at the emitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If bipolar transistors are used in the bandgap voltage reference circuit, then the reference voltage stability over temperature is achieved, but significant low-frequency noise is introduced
Solution Approach 1:
The patent extracts and removes the noise-generating base resistors from the circuit configuration. By eliminating these resistors that convert transistor noise into voltage noise, the harmful low-frequency noise is removed while preserving the temperature stability function provided by the bipolar transistors and ΔVbe/R circuit.
Solution Approach 2:
The patent inverts the conventional approach by connecting the emitters of the bipolar transistors directly to the amplifier inputs without intervening base resistors. This inversion of the typical resistor-based noise filtering approach achieves noise reduction by eliminating the noise conversion mechanism rather than by adding filtering components.
2Object-generated harmful factors
If base resistors are added to reduce noise, then low-frequency noise is minimized, but current consumption increases
Solution Approach 1:
The patent extracts and eliminates the base resistors from the circuit, thereby removing the source of excess current consumption associated with these resistors. The noise reduction objective is achieved without the penalty of increased current draw that would result from adding resistive noise-filtering components.
3Object-generated harmful factors
If transistor size is increased to reduce noise, then low-frequency noise is reduced, but the circuit area increases
Solution Approach 1:
The patent removes the base resistors that would otherwise be necessary to achieve noise reduction through conventional means. This extraction allows the circuit to achieve low noise performance without increasing transistor sizes or consuming additional circuit area for resistive components.
4Object-generated harmful factors
If conventional noise reduction methods are applied, then low-frequency noise is minimized, but design complexity increases
Solution Approach 1:
The patent achieves noise reduction through the simple act of removing base resistors from the circuit configuration. This minimalist approach avoids the design complexity of conventional noise reduction techniques that would require additional components, complex biasing networks, or sophisticated transistor sizing schemes.
Solution Approach 2:
Instead of adding complex noise-filtering infrastructure, the patent inverts the approach by eliminating the noise-conversion path through resistor removal. This simplifies the design while achieving the noise reduction objective that conventional methods would accomplish through added complexity.
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 reduces low-frequency noise without increasing power consumption, transistor area, or design complexity, while maintaining stability over temperature changes, making the circuit suitable for noise-sensitive applications.
Implementation Method 1
a ΔVbe/R circuit portion with first and second current path from first and second terminals through first and second bipolar transistors, respectively. The first and second bipolar transistors have different emitter areas
Implementation Method 2
The amplification circuit portion provides a current to each of the first and second terminals of the ΔVbe/R circuit portion and changes the current in response to a voltage difference between the first and second terminals of the ΔVbe/R circuit portion
Data Source
AI summary
A bandgap reference circuit includes a ΔVbe/R circuit portion and an amplification circuit portion. The ΔVbe/R circuit portion has a first and second current path from first and second terminals through first and second bipolar transistors, respectively. The first and second bipolar transistors have different emitter areas and the second path has a resistor. The amplification circuit portion provides a current to each of the first and second terminals of the ΔVbe/R circuit portion and changes the current in response to a voltage difference between the first and second terminals of the ΔVbe/R circuit portion. The ΔVbe/R circuit portion also has first and second base resistors connected to bases of the first and second bipolar transistors, respectively.