Low-Voltage Bandgap Current Architecture With Fewer Bipolar Devices
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Solution Overview
Problem
Conventional bandgap reference circuits are complex, costly, and prone to errors due to the large number of components, particularly bipolar transistors, which contribute to inaccuracies in generating reference currents and voltages, especially under varying temperature conditions.
Innovation Solution
A low voltage BiCMOS self-biased bandgap reference architecture that uses only two differently-sized bipolar transistors and eleven FET transistors arranged in five current branches to generate a bandgap reference voltage and current, eliminating the need for additional bipolar transistors and operational amplifiers, thereby reducing component count and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bandgap reference circuits use multiple bipolar transistors and operational amplifiers to generate reference currents, then the reference voltage can be generated, but the circuit complexity and component count increase significantly
Solution Approach 1:
The patent extracts and eliminates the operational amplifier from the conventional bandgap reference circuit topology. By using a direct current mirror configuration with bipolar transistors Q1 and Q2, the circuit achieves reference current generation without requiring an operational amplifier, thereby reducing component count while maintaining accuracy through precise current mirroring ratios
Solution Approach 2:
The patent merges the functions of multiple components into a streamlined configuration. The current mirror directly combines the reference current generation and temperature compensation functions that in conventional circuits are separated across multiple transistors and operational amplifiers, achieving the same reference voltage output with fewer components
2Stability of the object's composition
If conventional bandgap reference circuits use large numbers of circuit components to compensate CTAT voltage, then temperature independence is achieved, but the size and cost of the circuit increase
Solution Approach 1:
The patent changes the operating parameters of the bipolar transistors by using different emitter areas (Q1 with area A1, Q2 with area A2) to create the necessary PTAT voltage difference. This area ratio approach replaces the need for multiple transistors with the same area that would require complex compensation networks, achieving temperature independence through controlled parameter variation
Solution Approach 2:
The bipolar transistors Q1 and Q2 serve multiple functions simultaneously: they generate the PTAT voltage difference through area mismatch, provide current mirroring action, and create the temperature compensation effect. This multi-functionality replaces the specialized components needed in conventional circuits for each function, reducing overall component count
3Reliability
If conventional bandgap reference circuits use multiple bipolar transistors to generate PTAT and CTAT currents, then the reference voltage can be generated, but manufacturing precision requirements increase due to mismatch errors
Solution Approach 1:
The patent applies local quality by giving the bipolar transistors Q1 and Q2 different emitter areas (A1 and A2) tailored to their specific functional requirements. Q1 has area A1 optimized for generating the reference current, while Q2 has area A2 optimized for temperature compensation. This localized optimization reduces the need for perfect matching across all transistors, as each transistor's dimensions are specifically tailored to its role
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
This approach results in a more accurate, temperature-independent bandgap reference with reduced component count, lower power consumption, and simplified design, capable of operating at low voltages (e.g., 1V or lower) with minimal temperature coefficient variation.
Implementation Method 1
a first current that is a proportional to absolute temperature (PTAT) and a second current that is inversely or complementary to absolute temperature (CTAT)
Implementation Method 2
a first current that is a proportional to absolute temperature (PTAT) and a second current that is inversely or complementary to absolute temperature (CTAT)
Implementation Method 3
which compensate the CTAT voltage (VBE) developed across the base-emitter voltage of a bipolar transistor by a factor K (close to 10) multiplied by the PTAT voltage (ΔVBE)
Data Source
AI summary
A low voltage bandgap reference circuit (200) is provided which includes a first current generator (202) having first and second circuit branches which include, respectively, first and second bipolar transistors having different sizing reference values for generating a first current at a first resistor that varies proportionally as a function of temperature; a second current generator (204, 205) having a third circuit branch which includes one or more field effect transistors and no bipolar transistors for generating a second current that varies inversely as a function of temperature; and a third circuit (206) connected to generate a bandgap reference current in response to the first current and the second current.