Bandgap Reference Circuit Self-Biased Amplifier Low Voltage Operation
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Solution Overview
Problem
Conventional bandgap reference circuits for low system voltage operations are complex, consume high power, and require a large layout area, with errors in temperature coefficients due to process mismatches and additional resistors, limiting their applicability to system voltages below 1V.
Innovation Solution
A bandgap reference circuit utilizing a self-biased operational transconductance amplifier and a feedback voltage amplifier to generate positive and negative temperature coefficient currents, reducing the need for a tail-current-source and additional resistors, thereby simplifying the circuit and reducing the required system voltage to 1V, while maintaining zero temperature coefficient output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bandgap reference circuit structure is used for low system voltage operations, then the reference voltage can be generated, but the circuit complexity increases and layout area increases
Solution Approach 1:
The patent removes the tail-current-source from the operational transconductance amplifier, extracting this component to simplify the circuit structure. This extraction eliminates the need for the tail-current-source while maintaining the amplifier's functionality through alternative current biasing methods, directly reducing circuit complexity
Solution Approach 2:
The patent combines the functions of multiple components into fewer elements. By integrating the current biasing function directly into the amplifier structure and merging the reference voltage generation path with the operational amplifier feedback path, the circuit achieves the same functionality with reduced component count and simplified structure
2Reliability
If conventional bandgap reference circuit structure is used for low system voltage operations, then the reference voltage can be generated, but the power consumption increases
Solution Approach 1:
By removing the tail-current-source component, the patent eliminates the continuous current path that contributes to power consumption. The alternative biasing method uses voltage control rather than continuous current, significantly reducing the static power consumption of the operational transconductance amplifier
Solution Approach 2:
The patent changes the operating parameters of the amplifier from current-biased operation to voltage-biased operation. This parameter change allows the amplifier to maintain its transconductance function while operating at much lower power levels, enabling efficient reference voltage generation at low system voltages
3Reliability
If conventional bandgap reference circuit structure is used for low system voltage operations, then the reference voltage can be generated, but the layout area increases
Solution Approach 1:
The removal of the tail-current-source and associated current mirror structures extracts unnecessary circuit elements that would occupy layout area. This extraction directly reduces the physical footprint of the reference circuit while maintaining its functional integrity
Solution Approach 2:
The patent merges the reference voltage generation function with the operational amplifier structure, eliminating separate dedicated circuits. This functional integration allows shared use of circuit elements and reduces the overall layout area required for the reference voltage generator
4Reliability
If additional resistors are used in conventional bandgap reference circuit, then the temperature coefficient can be adjusted, but the circuit complexity increases and errors increase due to process mismatches
Solution Approach 1:
The patent extracts and removes the additional resistors from the circuit structure. By eliminating these passive components, the circuit achieves temperature coefficient adjustment through active device parameters and feedback control, reducing both complexity and sensitivity to process variations
Solution Approach 2:
The patent changes from resistor-based temperature compensation to a method using transistor parameter relationships and feedback control. This parameter change eliminates dependence on precise resistor matching, reducing errors from process mismatches while maintaining temperature coefficient adjustability through device geometry ratios
5Reliability
If conventional bandgap reference circuit structure is used, then the reference voltage can be generated, but the required system voltage must be at least 1.2V
Solution Approach 1:
The patent changes the voltage headroom requirements by modifying the amplifier structure and biasing method. The removal of the tail-current-source and adoption of voltage-biased operation reduces the minimum voltage requirement from 1.2V to 1V, expanding the adaptability to low-voltage systems
Solution Approach 2:
The operational transconductance amplifier is configured to self-bias, eliminating the need for external current sources and complex biasing circuits. This self-service mechanism allows the amplifier to maintain proper operation with minimal external voltage headroom, enabling functionality at system voltages as low as 1V
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 reduces circuit complexity, power consumption, and layout area, while minimizing errors caused by component mismatches, enabling efficient operation at lower system voltages with improved temperature coefficient stability.
Implementation Method 1
a positive temperature coefficient current ID can be generated through a base-to-emitter voltage difference VBE2−VBE1 which is generated by an area difference between bipolar junction transistors Q1 and Q2
Implementation Method 2
a feedback voltage amplifier, for amplifying the negative temperature coefficient control voltage, and outputting a reference voltage to the input pair for feedback, to generate a first negative temperature coefficient current
Data Source
AI summary
The present invention discloses a bandgap reference circuit. The bandgap reference circuit includes an operational transconductance amplifier, and a reference generation circuit. The operational transconductance amplifier includes a self-biased operational transconductance amplifier, for utilizing an area difference between bipolar junction transistors of an input pair to generate a first positive temperature coefficient current to bias the input pair, and generating a positive temperature coefficient control voltage and a negative temperature coefficient control voltage; and a feedback voltage amplifier, for amplifying the negative temperature coefficient control voltage, and outputting a reference voltage to the input pair for feedback, to generate a first negative temperature coefficient current. The reference generation circuit generates a summation voltage or a summation current according to the positive temperature coefficient control voltage and the negative temperature coefficient control voltage.