Low Drift Voltage Reference Using Zener and CTAT Compensation
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Solution Overview
Problem
Traditional voltage references exhibit instability over time due to drift issues primarily attributed to the CTAT voltage component, which is dependent on various process parameters, leading to fluctuations in temperature and power supply variations.
Innovation Solution
A voltage reference is created by combining a zener diode with a CTAT component, generated by a negative base-emitter voltage difference from multiple bipolar transistors operating at different collector current densities, to produce a compound voltage that is first-order compensated against temperature variations, thereby reducing drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a traditional voltage reference using CTAT component is used, then temperature compensation is achieved, but drift and instability occur over time
Solution Approach 1:
The patent combines a zener diode (providing PTAT voltage) with a CTAT voltage component in a single voltage reference circuit. The zener diode's stable voltage output with PTAT characteristics compensates for the drift issues of traditional CTAT-based references, achieving both temperature compensation and long-term stability through the merged configuration
Solution Approach 2:
The voltage reference uses a composite structure combining different semiconductor components (zener diode and bipolar transistors) with complementary temperature coefficients. This composite approach integrates materials and devices with opposing thermal characteristics to create a reference voltage that remains stable across temperature variations while maintaining low drift
2Temperature
If CTAT voltage component is used for temperature compensation, then temperature variations are compensated, but drift is introduced due to process parameter dependence
Solution Approach 1:
The patent changes the operating parameters of the zener diode and bipolar transistors to optimize the voltage reference performance. By adjusting the zener voltage selection and transistor current densities, the circuit achieves first-order temperature compensation while minimizing sensitivity to process variations through careful parameter selection rather than relying on precise manufacturing tolerances
3Reliability
If zener diode is combined with CTAT component, then drift is reduced, but circuit complexity increases
Solution Approach 1:
The voltage reference circuit is segmented into distinct functional blocks: a zener diode section for generating the base reference voltage, a bipolar transistor section for temperature compensation, and a buffering section. This segmentation allows each component to perform its specific function efficiently while maintaining overall circuit simplicity and modularity
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 solution results in a stable voltage reference with very low drift characteristics, maintaining consistency over a wide temperature range and power supply variations, with improved long-term stability and reduced noise, non-linearity, and power supply rejection ratio.
Implementation Method 1
The PTAT component is desirably generated by biasing a zener diode with bias current. As a result the output of the zener diode has a PTAT form that will increase with increases in absolute temperature.
Implementation Method 2
The CTAT component is generated by a negative base emitter voltage difference resultant from combining multiple bipolar transistors operating at different collector current densities.
Data Source
AI summary
Circuits and method for providing voltage reference circuits that include low drift over time and lower operating voltages are provided. Generally, it is desirable that a reference circuit provide an accurate and precise reference over time. The voltage reference circuits described can provide for good long term stability, operation at lower voltages than prior designs, consistent output voltage with reduced variability due to process changes and mismatches, low noise in the reference voltage, and other advantages.