Bandgap Voltage Generator Non-Linear Temperature Compensation
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Solution Overview
Problem
Existing bandgap voltage generators exhibit non-linear temperature dependence due to a non-linear component in the CTAT voltage, making it challenging to achieve a voltage that is perfectly independent of temperature.
Innovation Solution
The introduction of a device with a core comprising two PN junctions with different current densities, coupled with resistive networks to attenuate the non-linear component of the bandgap voltage, where the base resistance of the transistor with the higher current density is increased using additional resistors, and a second resistive network with lower resistance is used to further reduce the curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional bandgap voltage generator circuits are used, then a bandgap voltage of about 1.25 volts is generated, but the voltage includes a non-linear temperature component that prevents perfect temperature independence
Solution Approach 1:
The patent introduces additional resistive networks that modify the temperature coefficient parameters of the voltage generator circuit. By carefully selecting resistance values, the circuit adjusts the weighting of PTAT and CTAT components to cancel out the non-linear temperature dependence, transforming the temperature characteristic parameter from non-linear to near-linear or flat.
Solution Approach 2:
The patent uses additional resistors as intermediary elements between the existing PTAT and CTAT voltage sources. These resistive networks act as mediators that combine multiple voltage components with different temperature dependencies in a weighted sum, allowing the non-linear components to cancel each other out while producing a stable bandgap voltage.
2Measurement precision
If components with different temperature coefficients are added to compensate for non-linear components, then temperature compensation is achieved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent makes the existing resistive networks serve dual functions: they continue to set the operating points for the PTAT and CTAT current sources while simultaneously providing temperature compensation through their combined effect. This multi-functionality eliminates the need for separate compensation components, reducing overall circuit complexity.
Solution Approach 2:
The patent merges the temperature compensation function with the existing voltage generation function by integrating additional resistors into the current flowing paths of the PTAT and CTAT circuits. Instead of adding separate compensation branches, the resistors are combined with the functional elements, creating a unified circuit that performs both voltage generation and temperature compensation.
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 effectively reduces the peak-to-trough amplitude of the bandgap voltage from potentially higher than 3 mV to less than 0.7 mV, achieving a more stable voltage output that is closer to being independent of temperature.
Implementation Method 1
the voltage difference between two PN junctions (for example, diodes or diode-connected bipolar transistors), the current densities of which are different, allows a current proportional to absolute temperature
Implementation Method 2
a voltage generator that is coupled to the two terminals of the core and configured to generate the bandgap voltage
Implementation Method 3
an equalizer that is configured to equalize the potentials at the first terminal and at the second terminal
Data Source
AI summary
An integrated electronic device includes a core having a first terminal and a second terminal. The core includes a first branch with a first diode-connected bipolar transistor coupled in series to a first resistor between the first terminal and a reference terminal intended to be supplied with a reference voltage, and a second branch with a second diode-connected bipolar transistor coupled between the second terminal and the reference terminal. The second diode-connected bipolar transistor has a current density higher than the first diode-connected bipolar transistor. The core also includes a first resistive network coupled between a base of the first diode-connected bipolar transistor and the reference terminal. An equalizer is configured to equalize potentials of the first terminal and of the second terminal and a voltage generator is coupled to the first and second terminals of the core and configured to generate the bandgap voltage.