Reference Bias Circuit Low Voltage Operation
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Solution Overview
Problem
Conventional bandgap bias circuits are ineffective at generating stable reference voltages and currents at low supply voltages below 1.2V and are sensitive to temperature variations, limiting their application in modern electronic systems with diverse functions and varying temperatures.
Innovation Solution
A reference bias generating circuit that includes a self-bias circuit, a basic bandgap circuit, a startup circuit, a temperature compensator with mirroring units for positive and negative temperature coefficient characteristics, and a reference current or voltage mirroring unit to stabilize the output and reduce temperature sensitivity, using a combination of transistors, diodes, and resistors to generate reference currents and voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional bandgap bias circuit is used, then a reference voltage can be generated, but it cannot operate at supply voltages below 1.2V and is sensitive to temperature variations
Solution Approach 1:
The patent changes the operating parameters of the bias circuit by using a startup circuit to initialize operation at very low voltages, and by designing the bandgap circuit to operate correctly at supply voltages below 1.2V. The temperature compensation mechanism adjusts parameters to maintain stability across temperature ranges, resolving the contradiction between low power consumption and reference voltage stability.
Solution Approach 2:
The startup circuit performs preliminary action by initializing the bias circuit operation before the main bandgap circuit can stabilize. It provides initial bias currents and voltages necessary for the circuit to begin operation at low supply voltages, enabling the reference voltage generation to start without requiring higher initial voltage conditions.
2Use of energy by moving object
If the supply voltage is reduced to lower power consumption, then battery efficiency improves, but the reference bias circuit cannot generate stable reference voltages
Solution Approach 1:
The bandgap bias circuit employs feedback mechanisms where the generated reference voltage is used to regulate and stabilize the operating point. The circuit automatically adjusts internal parameters to maintain precise reference voltage output even at reduced supply voltages, achieving both low power consumption and high voltage precision simultaneously.
Solution Approach 2:
The circuit changes its operating parameters dynamically to maintain reference voltage precision at low supply voltages. By adjusting bias currents and utilizing temperature compensation, the circuit adapts its parameters to preserve manufacturing precision requirements while operating in low-voltage, low-power conditions.
3Reliability
If temperature compensation is added to reduce temperature sensitivity, then reference voltage stability improves, but circuit complexity increases
Solution Approach 1:
The temperature compensation function is merged with the main bandgap bias circuit rather than being implemented as a separate auxiliary system. The compensation mechanisms are integrated into the core circuit architecture, sharing common components and signal paths, which reduces overall circuit complexity while maintaining temperature stability.
Solution Approach 2:
The bias circuit is designed with multi-functionality where certain components serve both the reference voltage generation and temperature compensation functions. This universal design approach allows a single circuit structure to achieve both temperature stability and reference voltage generation without requiring additional dedicated compensation circuitry.
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 provides stable reference currents and voltages that are less sensitive to temperature variations and can operate at supply voltages lower than 1.2V, reducing power consumption and chip area while maintaining performance across temperature changes.
Implementation Method 1
a voltage ΔVBE applied to a first resistor RR1 is a difference between a base-emitter voltage VBE1 of the first bipolar junction transistor Q1 and a base-emitter voltage VBE2 of the second bipolar junction transistor Q2
Implementation Method 2
a base-emitter voltage VBE3 between the emitter and base of the third bipolar junction transistor Q3
Implementation Method 3
The voltage V1 applied to the both terminals of the second resistor RR2 can be expressed as Eq. 1 based on the Ohm's law. V1=I3×RR2
Data Source
AI summary
A reference current bias circuit includes a self-bias circuit configured to provide a bias current to an amplifier; a basic bandgap circuit coupled to inputs of the amplifier; a startup circuit configured to support an initial operation of the amplifier; a temperature compensator configured to include a first mirroring unit for mirroring current according to a positive temperature coefficient characteristic from the basic bandgap circuit; and a second mirroring unit for mirroring current according to a negative temperature coefficient characteristic from the basic bandgap circuit, and to provide a reference current by combining the current of the first mirroring unit and the current of the second mirroring unit; and a reference current mirroring unit configured to generate reference current biases based on the reference current from the temperature compensator.