Bandgap Reference Circuit With PTAT3 Biasing Current
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Solution Overview
Problem
Conventional bandgap reference circuits exhibit significant temperature drift over a wide temperature range, which is not adequately addressed by existing solutions, particularly in high-performance applications where lower drift values are required, and current compensation techniques are complex and costly.
Innovation Solution
A circuit design incorporating a proportional-to-absolute-temperature (PTAT) current generator and a cascaded arrangement of p-n junctions with a differential stage, which produces a bandgap reference voltage with minimal temperature drift by utilizing a PTAT3 biasing current, eliminating the need for complex curvature compensation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bandgap reference circuits are used, then voltage reference is provided, but temperature drift is significant
Solution Approach 1:
The patent changes the temperature dependence parameter of the biasing current from linear PTAT (proportional to absolute temperature) to cubic PTAT (proportional to absolute temperature cubed). This parameter change allows the circuit to compensate for the quadratic temperature drift of the bandgap voltage, achieving much lower temperature drift without requiring complex curvature compensation circuits. The cubic PTAT current is generated by cascading three p-n junctions with identical temperature coefficients.
Solution Approach 2:
The patent introduces a cubic PTAT current as an intermediary element that mediates between the temperature variation and the bandgap voltage. This cubic PTAT current serves as a compensating signal that counteracts the temperature drift, enabling the circuit to achieve low temperature drift performance without direct complex compensation mechanisms.
2Reliability
If curvature compensation circuits are added to reduce temperature drift, then temperature drift is reduced, but manufacturing cost and test time increase
Solution Approach 1:
By changing the biasing current temperature dependence to cubic PTAT, the patent eliminates the need for complex curvature compensation circuits that would otherwise be required to achieve low temperature drift. This parameter change simplifies the circuit architecture, reducing manufacturing complexity and test time while achieving superior temperature drift performance of approximately 0.55 ppm/°C.
3Reliability
If complex curvature compensation circuits are implemented, then temperature drift is reduced, but manufacturing cost increases
Solution Approach 1:
The patent achieves low temperature drift by changing the biasing current to cubic PTAT, which eliminates the need for complex curvature compensation circuits. This approach reduces manufacturing cost by simplifying the circuit architecture while maintaining excellent temperature drift performance, making the solution more economically viable for high-performance applications.
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 achieves a temperature drift of around 0.55 ppm/°C, significantly lower than conventional designs, with reduced manufacturing costs and test times due to simplified circuitry, and allows for flexibility in integration with existing bandgap reference circuits.
Implementation Method 1
the output from the differential stage is provided by the sum (with sign) of a VBE, though which a cubic PTAT biasing current flows, plus a PTAT voltage across the feedback resistor R/N, resulting in a bandgap reference VBG with a (very) small temperature drift (TD)
Data Source
AI summary
A first current proportional to absolute temperature flows in a first current line through a first p-n junction and a second p-n junction arranged in series. A cascaded arrangement of p-n junctions is coupled to the second p-n junction and includes a further p-n junction with a current flowing therethrough that has a third order proportionality on absolute temperature. A differential circuit has a first input coupled to the further p-n junction and a second input coupled to a current mirror from the first p-n junction, with the differential circuit configured to generate a bandgap voltage with a low temperature drift from a sum of first voltage (that is PTAT) derived from the first current and a second voltage (that is PTAT3) derived from the third current.