MOSFET PTAT-CTAT Voltage Reference for Low-Voltage Accuracy
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Solution Overview
Problem
Existing voltage reference circuits, particularly in low-voltage applications, face challenges in achieving high accuracy and low temperature coefficient performance due to limitations in bipolar junction transistor (BJT) technology, necessitating a solution that utilizes metal-oxide semiconductor (MOS) based technology for temperature-independent voltage references.
Innovation Solution
The implementation of a voltage reference circuit that combines proportional-to-absolute-temperature (PTAT) and complementary-to-absolute-temperature (CTAT) circuits using metal-oxide-semiconductor field-effect transistors (MOSFETs) to generate a substantially temperature-independent voltage output, offsetting temperature-induced variations through the interaction of PTAT and CTAT circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BJT-based temperature compensation circuits are used, then temperature compensation capability is improved, but device complexity and manufacturing constraints increase due to BJT or diode cut-in voltages
Solution Approach 1:
The patent substitutes BJT-based temperature compensation circuits with MOSFET-based circuits. Specifically, it replaces the mechanical/electrical characteristics of BJT transistors and diodes with MOSFET transistors that operate without cut-in voltage constraints, thereby simplifying the device structure while maintaining temperature compensation capability. The MOSFET-based differential pair circuit achieves temperature independence without requiring complex BJT biasing networks.
Solution Approach 2:
The patent changes the operating parameters by using MOSFETs instead of BJTs, exploiting the different electrical characteristics of MOSFETs (zero cut-in voltage, voltage-controlled operation) compared to BJTs (current-controlled, fixed cut-in voltage). This parameter change enables temperature compensation with simpler circuit topology and eliminates the constraints imposed by BJT cut-in voltages.
2Use of energy by moving object
If low voltage reference circuits are implemented, then power consumption is reduced, but accuracy and temperature coefficient performance deteriorate due to BJT technology limitations
Solution Approach 1:
The patent replaces BJT-based low voltage reference circuits with MOSFET-based circuits. The MOSFET differential pair configuration operates efficiently at low voltages while maintaining high accuracy through its inherent symmetry and matching characteristics. The substitution eliminates the accuracy degradation caused by BJT cut-in voltage variations and enables precise voltage referencing in low-power applications.
Solution Approach 2:
The patent uses matched MOSFET pairs (M1, M2) with identical geometries and characteristics to create a differential configuration that copies and cancels temperature-dependent parameters. This copying approach through differential signaling maintains accuracy while operating at low voltages, as the matched devices replicate each other's behavior and differential processing eliminates common-mode temperature effects.
3Ease of manufacture
If MOSFET-based voltage reference circuits are used, then ease of manufacture and adaptability to low voltage are improved, but temperature independence must be achieved through complex PTAT and CTAT circuit combinations
Solution Approach 1:
The patent merges PTAT (proportional-to-absolute-temperature) and CTAT (complementary-to-absolute-temperature) circuit functions into a unified MOSFET-based differential reference architecture. The differential pair inherently provides both PTAT and CTAT components through its operation, combining temperature compensation mechanisms in a single integrated structure rather than requiring separate circuit blocks. This merging simplifies manufacturing while achieving temperature independence.
Solution Approach 2:
The MOSFET differential pair circuit serves multiple functions simultaneously: it provides voltage reference, temperature compensation, and low-voltage operation capability. The same circuit topology achieves all these goals through the universal MOSFET device characteristics, eliminating the need for separate dedicated circuits for each function and reducing overall device complexity despite the multi-functional requirements.
Data Source
AI summary
Systems and methods are provided for generating a temperature compensated reference voltage. A temperature compensation circuit may include a proportional-to-absolute temperature (PTAT) circuit, and a complementary-to-absolute temperature (CTAT) circuit, with the PTAT circuit and the CTAT circuit including at least one common metal-oxide-semiconductor field-effect transistor (MOSFET) and being configured to collectively generate a reference voltage in response to a regulated current input. The PTAT circuit may be configured to produce an increase in magnitude of the reference voltage with an increase of temperature, and the CTAT circuit may be configured to generated a decrease in magnitude of the reference voltage with the increase of temperature, wherein the increase in magnitude of the reference voltage produced by the PTAT circuit is at least partially offset by the decrease in magnitude of the reference voltage produced by the CTAT circuit.