MOSFET Voltage Reference Circuit for Low-Voltage Temperature Stability
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Solution Overview
Problem
Modern semiconductor manufacturing processes face challenges in maintaining stable voltage reference circuits due to variations in manufacturing process, power supply voltage, and temperature, especially when bipolar junction transistors (BJTs) are unavailable or power supply voltage levels are insufficient, leading to sensitivity to noise and mismatch in circuit elements.
Innovation Solution
A MOSFET-based differential pair architecture with asymmetric transistors and differential feedback is employed, using resistive voltage dividers and current mirrors to generate reference voltages with minimal temperature variation, allowing operation at lower power supply voltages and without BJTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If bipolar junction transistors (BJTs) are used in voltage reference circuits, then temperature stability is improved, but device availability and power supply compatibility deteriorate
Solution Approach 1:
The patent replaces bipolar junction transistors (BJTs) with MOSFETs in the voltage reference circuit. This substitution eliminates the need for bipolar devices while maintaining the temperature stability function through the use of MOSFET-based differential pairs and asymmetric transistor configurations that compensate for temperature variations.
Solution Approach 2:
The patent changes the device parameter from BJT to MOSFET technology, enabling operation at lower power supply voltages (down to 1.0V) while maintaining temperature stability through carefully designed asymmetric transistor ratios and feedback mechanisms that compensate for temperature effects in the MOSFET regime.
2Device complexity
If conventional symmetric differential pair architecture is used, then circuit simplicity is improved, but sensitivity to mismatch and noise deteriorates
Solution Approach 1:
The patent introduces asymmetric transistor sizing in the differential pair configuration, where the transistors have different width-to-length ratios. This asymmetry is deliberately designed to compensate for process variations and mismatch effects, improving reliability while maintaining reasonable circuit simplicity. The asymmetric design also helps reduce noise sensitivity through differential cancellation mechanisms.
3Measurement precision
If voltage reference circuits are designed for high precision, then measurement precision is improved, but sensitivity to power supply noise and process variation worsens
Solution Approach 1:
The patent employs feedback mechanisms where the voltage reference circuit uses a portion of its own output or related signals to adjust and stabilize its operation. This feedback compensates for power supply noise and process variations, maintaining high precision voltage references even in the presence of these harmful factors. The feedback loops actively counteract disturbances to preserve reference accuracy.
Data Source
AI summary
A voltage reference circuit included in a computer system includes an asymmetric differential amplifier circuit that includes two metal-oxide semiconductor (MOS) transistors with different threshold voltages and different current densities. The voltage reference circuit also includes a driver circuit that generates, using a control signal, an output current that is used by a divider circuit to generate a reference voltage and a feedback voltage. The reference voltage and the feedback voltage are used by the asymmetric differential amplifier circuit to generate the control signal.