Low-Voltage Band-Gap Voltage Reference Circuit Using NMOS Input Pair
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Solution Overview
Problem
Existing band-gap voltage reference circuits require high minimal input voltages, which can be disadvantageous due to amplified offset issues, especially when using PMOS input pair structures, and often struggle with temperature stability.
Innovation Solution
A low-voltage band-gap voltage reference circuit incorporating an NMOS input pair operational amplifier, current mirror, adaptive adjustment circuit, and BJT branches to equalize voltages and generate a temperature-independent output voltage, with a minimal input voltage requirement of approximately 1.2V, using deep negative feedback and adaptive base voltage adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PMOS input pair structure is used in operational amplifier, then voltage reference circuit can operate, but minimal input voltage requirement increases and offset is amplified
Solution Approach 1:
The patent inverts the conventional approach by using NMOS input pair instead of PMOS, and by inverting the traditional bandgap structure to achieve low-voltage operation. This inversion allows the circuit to operate with minimal input voltage of approximately 1.2V while maintaining operational amplifier performance.
Solution Approach 2:
The patent changes key parameters including switching from PMOS to NMOS input pair, adjusting the bandgap structure, and modifying biasing conditions to enable low-voltage operation. These parameter changes reduce the minimal input voltage requirement from conventional higher values to approximately 1.2V.
2Stability of the object's composition
If deep negative feedback is used to equalize voltages, then voltage stability improves, but circuit complexity increases
Solution Approach 1:
The patent employs deep negative feedback through the operational amplifier to equalize voltages at the upper ends of the two BJT branches. This feedback mechanism ensures voltage stability and maintains the bandgap reference voltage independence from temperature and supply voltage variations.
Solution Approach 2:
The circuit is segmented into distinct functional blocks including operational amplifier, current mirror, bandgap output circuit, adaptive adjustment circuit, and two BJT branches. This segmentation allows each block to perform its specific function while working together to achieve overall voltage stability.
3Temperature
If adaptive adjustment circuit is added to adjust base voltage of BJT, then temperature stability improves, but device complexity increases
Solution Approach 1:
The patent introduces dynamic adaptation by allowing the base voltage of common base BJTs to be adjustably controlled based on operating conditions. The adaptive adjustment circuit dynamically modifies bias voltages to compensate for temperature variations, ensuring stable bandgap reference voltage across different temperatures.
Solution Approach 2:
The adaptive adjustment circuit changes biasing parameters (base voltages of BJT branches) in response to temperature and operating conditions. This parameter adjustment enables the circuit to maintain temperature-independent output voltage despite environmental variations.
Data Source
AI summary
The present application discusses low voltage band-gap voltage reference circuit and methods. In an example the circuit can include a current mirror, an operational amplifier adopting an N-Metal-Oxide-Semiconductor (NMOS) input pair structure, a band-gap output circuit, an adaptive adjustment circuit; and two branches of Bipolar Junction Transistor (BJT). The current mirror can be configured to receive an output signal of the operational amplifier and to provide a current to the two branches of BJT. The operational amplifier can be configured to differentially input voltages at the upper ends of the two branches of BJT, to generate the output signal to the current mirror, and to equalize the voltages at the upper ends of the two branches of BJT using a deep negative feedback.