Temperature Sensor Bias Circuit With Poly-Resistor Flicker Noise Reduction
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Solution Overview
Problem
Temperature sensor arrangements face limitations in long-term stability and accuracy due to low-frequency flicker noise in biasing currents, which is challenging to address with existing solutions that often require complex implementations and trade-offs in circuit size, power consumption, and complexity.
Innovation Solution
Incorporating a poly-resistor connected between the bandgap voltage generator and the semiconductor junction to reduce low-frequency flicker noise, along with a chopper amplifier and source follower output stage to stabilize the bandgap voltage generator, allowing for accurate temperature measurement with reduced area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional biasing current sources are used, then the temperature sensor can operate, but flicker noise at low frequency occurs which limits long-term stability and accuracy
Solution Approach 1:
The patent extracts the problematic biasing current source from the temperature sensor arrangement and replaces it with a poly-resistor connected to a bandgap voltage generator. This removal of the conventional current source eliminates the primary source of low-frequency flicker noise while maintaining the necessary biasing function through the poly-resistor's inherent properties.
Solution Approach 2:
The patent changes the electrical parameters of the biasing network by using a poly-resistor with specific resistance characteristics instead of an active current source. This parameter change transforms the noise profile from high flicker noise to low flicker noise, thereby improving measurement accuracy and long-term stability.
2Measurement precision
If chopper-stabilized OTA or chopping methods are implemented to reduce flicker noise, then flicker noise is reduced, but circuit complexity, size, and power consumption increase
Solution Approach 1:
The patent employs a simple poly-resistor component instead of complex chopper-stabilized circuits. The poly-resistor is a passive, inexpensive element that inherently provides low flicker noise without requiring active stabilization mechanisms, thereby dramatically simplifying the circuit while achieving the desired noise performance.
Solution Approach 2:
The poly-resistor acts as an intermediary element between the bandgap voltage generator and the temperature sensing junction. It provides the necessary biasing current while introducing minimal noise, serving as a simple mediator that eliminates the need for complex noise reduction circuits.
3Measurement precision
If chopper-stabilized bandgap reference circuit is used to handle flicker noise in Voff and Vref, then flicker noise in reference voltages is reduced, but additional circuit area and power are required
Solution Approach 1:
The poly-resistor serves multiple functions: it provides biasing current to the temperature sensing junction, acts as a noise filter due to its low flicker noise characteristics, and eliminates the need for separate chopper-stabilized reference circuits. This multi-functionality reduces the overall circuit area while maintaining measurement accuracy.
4Measurement precision
If conventional biasing current sources are used, then the temperature sensor can function, but power consumption is high due to additional circuitry
Solution Approach 1:
The patent replaces power-hungry active current sources with a simple poly-resistor that consumes minimal power. The passive nature of the poly-resistor eliminates the need for continuous power supply to active stabilization circuits, thereby significantly reducing overall power consumption while maintaining low flicker noise performance.
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 proposed solution significantly reduces flicker noise, improves linearity, and simplifies implementation by eliminating the need for chopping, resulting in enhanced accuracy and lower power consumption compared to conventional biasing current sources.
Implementation Method 1
the flicker noise at low frequency is greatly reduced in the sensor, which allows an accurate measurement of the temperature. Moreover, the area consumption of the proposed new solution is much lower than that of the conventional biasing current sources, since it only requires at least one poly-resistor. Additionally, the power consumption in the proposed solution is much lower than that of the conventional biasing current sources
Implementation Method 2
a bandgap voltage generator 8. A current source Ib is used to bias a bipolar semiconductor junction 2. The bipolar semiconductor junction 2 is for example a diode-connected substrate pnp type transistor. The resulted voltage, Vbe, has complementary to absolute temperature (CTAT) characteristics
Implementation Method 3
Temperature sensor circuits are used in some applications to monitor the environment. In some other applications, such sensor circuits can be used to tune parameters of an external circuit in order to compensate its nonidealities upon temperature changes. Generally, such sensor circuits include a semiconductor junction for temperature sensing
Data Source
AI summary
A temperature sensor arrangement (10), including a bandgap voltage generator (12), which is configured to provide an output voltage (Vbg); at least one semiconductor junction (14) for temperature sensing, which is biased by a biasing current flowing through said semiconductor junction (14); and at least one poly-resistor (Rb3) which is connected between the output (23) of the bandgap voltage generator (12) and the semiconductor junction (14), thereby providing said biasing current from the bandgap voltage generator (12) to the semiconductor junction (14).