Bandgap Voltage Reference Circuit Offset Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bandgap voltage reference circuits face challenges in maintaining stability and accuracy, particularly with extreme variability of common-mode voltage due to temperature changes, which can lead to operational amplifier malfunction when supply voltage is low, such as in advanced CMOS technologies.
Innovation Solution
A bandgap voltage reference circuit design that incorporates an operational amplifier with n-channel MOS transistors and a control circuit using capacitive means and biasing to manage common-mode voltage, ensuring the operational amplifier operates within the saturation region, even at low supply voltages, and includes an offset management circuit to compensate for offset voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the operational amplifier is designed to handle large common-mode voltage excursions, then the voltage reference circuit can operate across temperature variations, but the operational amplifier may be forced into triode operation region and malfunction when supply voltage is reduced
Solution Approach 1:
The patent divides the operational amplifier into two separate functional blocks: a first operational amplifier dedicated to generating the bandgap voltage reference, and a second operational amplifier dedicated to managing common-mode voltage. This segmentation allows each amplifier to be optimized for its specific function, preventing the first amplifier from malfunctioning due to excessive common-mode voltage variations.
Solution Approach 2:
The patent introduces a second operational amplifier as an intermediary component that actively manages and controls the common-mode voltage at the input terminals of the first operational amplifier. This intermediary ensures that the common-mode voltage remains within the safe operating range of the first amplifier, preventing triode region operation while maintaining temperature adaptability.
2Use of energy by moving object
If n-channel MOS transistors are used in the operational amplifier input stage, then the circuit can operate at low supply voltages, but offset voltage becomes a significant issue affecting accuracy
Solution Approach 1:
The patent employs offset compensation techniques using feedback mechanisms. The second operational amplifier monitors and compensates for offset voltages in the first operational amplifier, ensuring that accuracy is maintained even when using n-channel MOS transistors at low supply voltages.
Solution Approach 2:
The patent changes the operating parameters of the operational amplifiers by introducing common-mode voltage control. By actively managing the common-mode voltage level, the circuit maintains proper transistor operation in the saturation region, which is critical for maintaining both low voltage operation and high accuracy.
Data Source
AI summary
An embodiment of a circuit includes first and second branches, an amplifier, a compensation circuit, and a bias unit. The first and second branches are respectively operable to generate first and second currents. The amplifier has a first amplifier input node coupled to the first branch, a second amplifier input node coupled to the second branch, an amplifier output node coupled to the first and second branches, and a first compensation node. The compensation unit is operable to provide a first offset-compensation signal to the first compensation node. And the first bias unit is operable to provide first and second bias signals to the first and second input nodes, respectively, such that the amplifier is operable to cause the first current to approximately equal the second current.