One-Volt Bandgap Reference Circuit Architecture
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Solution Overview
Problem
Conventional bandgap circuits generate a temperature-invariant output voltage typically around 1.2V, which is not adjustable and not lower than this value, limiting their application in generating stable voltages across a wide range of temperatures.
Innovation Solution
A bandgap reference circuit with a one-volt architecture is designed using three transistors and resistors, where a 'super-PTAT' current is generated by subtracting a CTAT current from a PTAT current, flowing through resistors to produce a temperature-compensated output voltage near 1.0V, achieved by adjusting the resistances in the feedback divider.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional bandgap circuits are used to generate temperature-invariant output voltage, then temperature stability is improved, but the output voltage is fixed around 1.2V and cannot be adjusted or lowered
Solution Approach 1:
The patent introduces a dynamic architecture where the output voltage can be adjusted by changing the feedback divider ratio while maintaining temperature compensation. The circuit transitions from a fixed 1.2V output to a variable output that can be set to 1.0V or other values by adjusting the feedback network, making the bandgap circuit adaptable to different voltage requirements while preserving temperature stability
Solution Approach 2:
The patent changes the output voltage parameter from the conventional 1.2V to a lower 1.0V by modifying the feedback divider configuration. This parameter change is achieved by adjusting the resistance values in the feedback network, allowing the output voltage to be tuned to desired values while maintaining the temperature-invariant characteristic through the super-PTAT current generation
2Stability of the object's composition
If conventional bandgap circuits generate 1.2V output, then temperature compensation is achieved, but the output voltage cannot be lowered below 1.2V for applications requiring lower voltages
Solution Approach 1:
The patent directly addresses this contradiction by changing the output voltage parameter from 1.2V to 1.0V through modified feedback divider design. The super-PTAT current generation mechanism maintains temperature compensation while the adjusted feedback network enables the lower output voltage level, allowing the circuit to operate at voltages below the conventional 1.2V threshold
3Adaptability or versatility
If the output voltage is adjusted in conventional bandgap circuits, then versatility is improved, but the temperature characteristic is affected
Solution Approach 1:
The patent employs a feedback mechanism where the output voltage is fed back through a configurable divider network to the input stage. This feedback loop maintains the temperature compensation relationship even when the divider ratio is changed to adjust the output voltage. The super-PTAT current generation ensures that temperature characteristics are preserved regardless of the feedback divider configuration, allowing independent adjustment of voltage level while maintaining temperature stability
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 circuit generates a stable output voltage close to 1.0V across a wide temperature range, with minimal temperature variation, allowing for adjustable output voltage without affecting the temperature characteristic, effectively addressing the limitations of conventional bandgap circuits.
Implementation Method 1
Bandgap circuits typically use two diodes to generate a proportional-to-absolute-temperature (PTAT) current
Implementation Method 2
A voltage across a diode (either one of the diodes used to generate the PTAT current or another diode) is typically complementary-to-absolute-temperature (CTAT), meaning the voltage decreases when the temperature increases
Implementation Method 3
The voltage across the diode and the voltage across the resistor collectively represent an output voltage of the bandgap circuit. Bandgap circuits routinely generate a steady, temperature invariant output voltage
Data Source
AI summary
A system includes a transistor coupled to a voltage rail, a first resistor coupled in series with the transistor, and a second resistor coupled in series with the first resistor. The system also includes a bandgap reference circuit operable to generate a bandgap reference voltage of less than 1.2 volts (such as one volt) between the first and second resistors. The bandgap reference circuit includes a diode configured to generate a complementary-to-absolute-temperature (CTAT) voltage and a third resistor configured to generate a first proportional-to-absolute-temperature (PTAT) voltage using a first current. The bandgap reference circuit also includes a current source configured to sink a CTAT current from the first current to generate a second current and a fourth resistor configured to generate a second PTAT voltage using the second current. A sum of the CTAT voltage, the first PTAT voltage, and the second PTAT voltage is less than 1.2 volts.