Bandgap Reference Circuit for Lower Minimum Operating Voltage
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Solution Overview
Problem
Conventional reference voltage generation circuits using the bandgap reference method struggle to further reduce the minimum operating voltage.
Innovation Solution
A reference voltage generation circuit is designed with a PTAT current generation unit and a CTAT current generation unit, utilizing current sources and resistors to generate reference voltages, with an output unit that combines these currents to achieve a lower minimum operating voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an operational amplifier is used in the reference voltage generation circuit, then the circuit stability and voltage addition accuracy are improved, but the minimum operating voltage increases and circuit area expands
Solution Approach 1:
The patent extracts and removes the operational amplifier component from the reference voltage generation circuit. By eliminating this high-voltage-requiring component, the circuit achieves lower minimum operating voltage while maintaining functionality through alternative current mirror and resistor-based voltage generation mechanisms
Solution Approach 2:
The patent changes the operating parameters of the circuit by using current mirror circuits with specific current ratios and resistor value selections to generate the reference voltage without requiring the high voltage headroom that operational amplifiers demand. This parameter optimization enables low-voltage operation while preserving circuit stability
2Measurement precision
If an operational amplifier is used in the reference voltage generation circuit, then the voltage addition accuracy is improved, but the circuit area increases
Solution Approach 1:
The patent removes the operational amplifier from the circuit configuration, thereby eliminating the large area that such an amplifier would occupy on the integrated circuit while achieving the same voltage addition function through compact current mirror and resistor networks
Solution Approach 2:
The patent uses current mirror circuits to replicate and add currents proportionally, achieving voltage addition accuracy without requiring physical operational amplifiers. The current mirrors copy reference currents and combine them through resistor networks, providing accurate voltage synthesis in a compact form
3Area of stationary object
If conventional current addition type method is used without operational amplifier, then the circuit area is reduced, but the minimum operating voltage cannot be further reduced
Solution Approach 1:
The patent optimizes the parameters of the current mirror circuit by selecting specific current ratios (such as 2:1 or 1:1 ratios) and resistor values that enable the circuit to operate at minimum voltages of 0.7V or lower, further reducing the operating voltage threshold beyond conventional designs
Solution Approach 2:
The patent segments the reference voltage generation into separate current generation paths (PTAT and CTAT current paths) that can be independently optimized for low-voltage operation, allowing each segment to be tuned for minimal voltage requirements while maintaining overall circuit functionality
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 circuit effectively lowers the minimum operating voltage while maintaining circuit stability and reducing circuit area, compared to conventional designs.
Implementation Method 1
a proportional to absolute temperature (PTAT) current generation unit including a first current source and a second current source which are connected in parallel to one of a power supply voltage and a ground voltage, a pair of bipolar transistors which is connected in parallel to a current mirror circuit including the first current source and the second current source, and a first resistor which is connected to an emitter of one of the pair of bipolar transistors
Implementation Method 2
a complementary to absolute temperature (CTAT) current generation unit which includes a third current source and a second resistor that are inserted in series between the power supply voltage and the ground voltage
Implementation Method 3
a reference voltage generation circuit of a bandgap reference method... a voltage addition type is a method of adding a proportional to absolute temperature (PTAT) voltage and a complementary to absolute temperature (CTAT) voltage
Data Source
AI summary
Circuitry that generates a constant reference voltage with reduced minimum operating voltage is disclosed. In one example, a PTAT current generation unit includes first and second current sources connected in parallel to one of a power supply voltage and a ground voltage, two bipolar transistors connected in parallel to a current mirror circuit including the current sources, and a first resistor which is connected to an emitter of one of the bipolar transistors. A CTAT current generation unit includes a third current source and a second resistor inserted in series between the power supply and ground voltages. A connection node between the third current source and the second resistor is connected in common to gates of the bipolar transistors. A reference voltage is output according to addition of a PTAT current supplied by the first and second current sources and a CTAT current supplied by the third current source.