Low-Voltage Reference Voltage Circuit With PTAT-CTAT Compensation
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Solution Overview
Problem
Existing reference voltage generator circuits face challenges in achieving high accuracy at low power supply voltages due to offset errors and temperature non-linearity, particularly when operating below the bandgap voltage of silicon.
Innovation Solution
A voltage generator circuitry is designed using bipolar transistors with common base electrodes, current mirror circuits, differential amplifiers, and a current-voltage conversion circuit, which cancels temperature-dependent effects by generating PTAT and CTAT currents, and adjusts resistor ratios to reduce temperature dependence and exclude offset voltage influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bandgap voltage reference circuit is used to achieve high accuracy, then measurement precision is improved, but the power supply voltage requirement increases (cannot operate below bandgap voltage)
Solution Approach 1:
The patent changes the operating parameters by using bipolar transistors with different emitter areas to generate PTAT and CTAT voltage components that can be combined to achieve a reference voltage lower than the traditional bandgap voltage while maintaining high accuracy through temperature compensation
Solution Approach 2:
The patent combines PTAT (proportional to absolute temperature) and CTAT (complementary proportional to absolute temperature) voltage components from bipolar transistors to create a composite reference voltage that operates below the bandgap voltage while canceling temperature dependence effects
2Stability of the object's composition
If bipolar transistors are used to generate PTAT and CTAT components, then temperature compensation is improved, but manufacturing precision requirements increase due to non-linearity
Solution Approach 1:
The patent applies local quality by using bipolar transistors with specifically designed different emitter areas to generate the required PTAT and CTAT components, where each transistor's local geometric property is optimized for its specific function in the temperature compensation scheme
Solution Approach 2:
The patent uses feedback through the combination of PTAT and CTAT voltage components to automatically compensate for temperature variations, where the temperature-dependent effects are fed back and canceled to maintain stable reference voltage output
3Measurement precision
If error amplifier offset is excluded to improve accuracy, then measurement precision is improved, but circuit complexity increases
Solution Approach 1:
The patent extracts and eliminates the error amplifier component from the traditional bandgap reference circuit, using direct bipolar transistor configurations to generate and combine PTAT and CTAT voltages without requiring offset-prone amplifying stages
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 circuitry achieves high accuracy and operates on a power supply voltage lower than the bandgap voltage, suppressing accuracy deterioration from temperature non-linearity and offset errors, with improved output voltage stability across temperature ranges.
Implementation Method 1
A reference voltage generator circuitry using a bandgap voltage of semiconductor is configured to cancel the temperature dependence by adding together a PTAT (proportional to absolute temperature) component of a voltage or current, which increases proportionally to the absolute temperature, and a CTAT (complementary proportional to absolute temperature) component of a voltage or current, which decreases proportionally to the absolute temperature
Implementation Method 2
The current-voltage conversion circuitry converts the sum current of the first and second currents into an output voltage
Data Source
AI summary
A voltage generator circuitry includes first to third bipolar transistors having commonly-connected base electrodes, first and second current mirror circuitries, first and second differential amplifiers; a first resistor; and a current-voltage conversion circuitry. The first current mirror circuitry supplies currents to the first to third bipolar transistors and to the current-voltage conversion circuitry. The second current mirror circuitry supplies currents to the first to third bipolar transistors, and s to the current-voltage conversion circuitry. The first and second differential amplifiers control the first and second current mirror. The current-voltage conversion circuitry converts a sum current of the first and second currents into an output voltage.