TMOS Amplification Interface for Common-Mode Rejection Calibration
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Solution Overview
Problem
Conventional measurement systems face challenges in effectively amplifying and processing signals from thermally isolated MOS (TMOS) sensors, particularly in rejecting common-mode signals and temperature variations, which affects the accuracy and reliability of temperature measurements.
Innovation Solution
An amplification interface is designed with a differential current integrator and PTAT bias-current generators, along with a regulation circuit and sample-and-hold circuit, to amplify the differential signal between two TMOS transistors while compensating for temperature variations and common-mode disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional amplifier circuit is used to amplify the measurement signal from TMOS sensors, then the signal amplification is achieved, but the common-mode signals and temperature variations cannot be effectively rejected, degrading measurement precision
Solution Approach 1:
The measurement system is segmented into two parallel paths: one path processes the signal from the exposed TMOS transistor (MEXP) while the other processes the signal from the blind TMOS transistor (MBLIND). This segmentation allows the system to separately capture the differential temperature signal and the common-mode temperature variations, enabling subsequent rejection of the common-mode components through differential processing.
Solution Approach 2:
The blind TMOS transistor (MBLIND) acts as an intermediary element that captures only the common-mode temperature variations without being exposed to the measured target. By introducing this intermediary sensor, the system can isolate and subsequently reject common-mode disturbances through differential amplification, improving the precision of the temperature measurement.
2Reliability
If the measurement system is designed to compensate for temperature variations and reject common-mode signals, then measurement reliability is improved, but the device complexity increases due to additional circuits
Solution Approach 1:
The differential amplifier circuit serves multiple functions simultaneously: it amplifies the small differential signal from the TMOS transistors, rejects common-mode temperature variations, and provides signal conditioning for subsequent processing. By making the amplifier multi-functional, the design achieves reliable temperature measurement without proportionally increasing overall system complexity.
Solution Approach 2:
The patent merges the signal amplification function with the common-mode rejection function into a single differential amplification stage. By combining these functions in one circuit block rather than using separate stages, the design achieves reliable measurement while minimizing the increase in device complexity.
3Measurement precision
If the amplification interface uses complex calibration procedures to account for process spread, then measurement accuracy is improved, but the ease of operation deteriorates
Solution Approach 1:
The measurement system performs self-calibration by utilizing the blind TMOS transistor (MBLIND) as an internal reference that automatically tracks process variations and temperature drifts. This self-service mechanism eliminates the need for external calibration equipment and complex manual procedures, maintaining high measurement accuracy while preserving ease of operation.
Solution Approach 2:
The system implements feedback through the blind TMOS transistor that continuously monitors the common-mode temperature variations and process drifts. This feedback information is automatically used by the differential amplifier to compensate for variations, achieving high measurement accuracy without requiring manual calibration interventions.
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
The solution enhances the accuracy and reliability of temperature measurements by effectively amplifying the differential signal and compensating for temperature variations, ensuring robustness against process spread and common-mode noise.
Implementation Method 1
a differential integrator, which comprises a first input terminal connected to the second node and a second input terminal connected to the first node
Implementation Method 2
PTAT bias-current generators, along with a regulation circuit and sample-and-hold circuit
Implementation Method 3
the TMOS is obtained with a suspended structure to help maximize thermal isolation for the remaining portion of the die in which it is obtained
Implementation Method 4
The small temperature variations of the device result in variations of the I-V (current-voltage) characteristic of the transistor itself
Data Source
AI summary
An amplification interface includes a drain of a first FET connected to a first node, a drain of a second FET connected to a second node, and sources of the first and second FETs connected to a third node. First and second bias-current generators are connected to the first and second nodes. A third FET is connected between the third node and a reference voltage. A regulation circuit drives the gate of the third FET to regulate the common mode of the voltage at the first node and the voltage at the second node to a desired value. A current generator applies a correction current to the first and/or second node. A differential current integrator has a first and second inputs connected to the second and first nodes. The integrator supplies a voltage representing the integral of the difference between the currents received at the second and first inputs.