Bandgap Reference Circuit With Feedback-Matched Resistors at Low Voltage
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Solution Overview
Problem
Existing bandgap reference voltage sources face challenges in generating stable reference voltages at reduced supply voltages below 1.2 Volts, particularly due to current mismatches caused by varying drain-to-source voltages and semiconductor process variations, leading to errors in temperature-compensated reference voltages.
Innovation Solution
The solution involves using a configuration with sets of resistors and control circuits to generate temperature-compensated currents and voltages, where negative feedback ensures consistent voltage drops across resistors, reducing current mismatches and errors in the reference voltage generation, and employing a method that replaces FETs with resistors to achieve better matching and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FETs are used for biasing the bandgap reference voltage, then the reference voltage can be generated, but current mismatches occur due to varying drain-to-source voltages and semiconductor process variations
Solution Approach 1:
The patent changes the operating parameters by reducing the drain-to-source voltage of the FETs through a modified circuit topology. By using a current mirror configuration with matched FETs and resistors, the circuit maintains equal voltages across series-connected resistor pairs, thereby reducing voltage variations and improving current matching accuracy while generating a stable reference voltage.
2Use of energy by moving object
If the supply voltage is reduced below 1.2 Volts, then power consumption is reduced and circuit size is reduced, but the bandgap reference voltage source cannot operate properly
Solution Approach 1:
The patent changes the operating voltage parameter by designing a bandgap reference circuit that can operate with supply voltages below 1.2V. The modified topology with reduced voltage drops across components and optimized current paths enables proper reference voltage generation even when the supply voltage is reduced, thereby reducing power consumption while maintaining reliability.
3Ease of manufacture
If semiconductor process variations occur, then manufacturing cost is reduced, but current mismatches increase leading to errors in reference voltage
Solution Approach 1:
The patent implements a feedback mechanism through the current mirror configuration and voltage comparison across matched resistor pairs. The circuit automatically compensates for process variations by adjusting the current distribution to maintain equal voltages across the resistor pairs, thereby reducing the impact of manufacturing variations on reference voltage accuracy.
Solution Approach 2:
The patent uses carefully selected resistor ratios and current mirror scaling factors to compensate for process variations. By changing the electrical parameters of the circuit components during design, the circuit achieves robustness against manufacturing variations while maintaining accurate current matching and reference voltage generation.
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 significantly reduces errors in the generated reference voltage, ensuring stability and accuracy over a defined temperature range, even at low supply voltages, by ensuring consistent currents and voltage drops across resistors, thereby improving the reliability of temperature-compensated reference voltage generation.
Implementation Method 1
a control circuit configured to generate a second voltage across the second set of one or more resistors, wherein the second voltage is based on the first voltage
Implementation Method 2
a first voltage is generated across the first set of one or more resistors based on the first temperature-compensated current
Data Source
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AI summary
An apparatus and method for generating a temperature-compensated reference voltage are disclosed. The apparatus generates substantially equal temperature-compensated currents by controlling (through negative feedback) voltages across separate resistors through which the currents flow, respectively. Two of the temperature-compensated currents are formed by combining (e.g., summing) a complementary to absolute temperature (CTAT) current (ICTAT) and a proportional to absolute temperature (PTAT) current (IPTAT). A reference voltage VREF is produced by configuring the other the temperature-compensated current to flow through an output resistor.