Stacked MOSFET Voltage Reference for Temperature Stability

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Solution Overview

Problem

Modern MOSFET-based bandgap voltage references suffer from significant temperature inaccuracy (15-20% 3σ) and are space-constrained in integrated circuits, limiting their application in precision devices.

Innovation Solution

A stacked gate device design using series-connected MOSFETs with varying threshold voltages, combined with a temperature coefficient trimming circuit, to stabilize the output voltage and reduce temperature sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If traditional MOSFET-based bandgap voltage references are used, then the circuit can be implemented in standard CMOS technology, but the temperature accuracy deteriorates with 15-20% 3σ variation

Engineering Contradiction:

ImproveCMOS compatibilityVSAvoidtemperature accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The voltage reference circuit is divided into multiple independent stacked gate devices (first stacked gate device, second stacked gate device, third stacked gate device) with different threshold voltages. Each device processes the reference voltage independently, and their outputs are combined to achieve temperature compensation. This segmentation allows the circuit to maintain CMOS compatibility while improving temperature accuracy through diverse device characteristics.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If stacked gate devices with different threshold voltages are used, then temperature coefficient accuracy improves, but device complexity increases

Engineering Contradiction:

Improvetemperature coefficient accuracyVSAvoidcircuit structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Different stacked gate devices are designed with specific local characteristics - the first device uses MOSFETs with first threshold voltages, the second device uses MOSFETs with second threshold voltages, and the third device uses MOSFETs with third threshold voltages. Each device is optimized for its specific function in the temperature compensation process, allowing the overall circuit to achieve high accuracy without requiring complete redesign of the entire system.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If multiple stacked gate devices are combined, then voltage stability improves, but area occupancy increases

Engineering Contradiction:

Improvevoltage stabilityVSAvoidcircuit area

Core Design Contradiction:

Stability of the object's compositionVSArea of stationary object

Solution Approach 1:

Multiple stacked gate devices with different threshold voltage characteristics are merged into a single integrated voltage reference circuit. The first, second, and third stacked gate devices are combined such that their individual contributions to voltage stability are preserved while their area occupancy is optimized through shared circuit elements and compact layout techniques.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS20250362701A1Voltage reference circuit

Publication Date: 2025.11.27 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A bandgap voltage reference circuit is provided. In one example, a cell includes a first device including a first plurality of MOSFETs connected in series The cell further includes a second device including a second plurality of MOSFETs connected in series. The second device connects in series with the first device. The second plurality of MOSFETs has a second Vt that is higher than the first Vt. The cell further includes a reference node connected between the first stack gate device and the second stack gate device.