Flipped-Gate Voltage Reference Circuit at Zero-Temperature Coefficient
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Solution Overview
Problem
Conventional voltage reference circuits using bipolar junction transistors (BJTs) and CMOS devices are susceptible to substrate noise, limiting their ability to provide a temperature-independent reference voltage.
Innovation Solution
A voltage reference circuit employing a flipped-gate transistor with an anti-doped gate electrode and a non-flipped-gate transistor, where the current ratio between them is adjusted to achieve a zero-temperature coefficient (ZTC) operating point, ensuring the reference voltage remains constant across various temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bipolar junction transistors (BJTs) are used to form bandgap references, then a reference voltage can be provided, but the circuit becomes sensitive to substrate noise and cannot achieve full isolation
Solution Approach 1:
The patent introduces an anti-doped gate electrode as an intermediary layer between the doped substrate and the transistor channel. This anti-doped gate acts as a mediator that repels majority carriers from the substrate, creating a protective barrier that isolates the transistor from substrate noise while maintaining proper transistor operation
Solution Approach 2:
The patent extracts the noise-isolation function from the traditional BJT structure by separating the gate doping from the substrate doping. The anti-doped gate electrode is extracted as a distinct functional layer that specifically addresses substrate noise isolation, allowing the transistor to operate independently from substrate interference
2Object-affected harmful factors
If CMOS devices are fabricated in triple well flow with reverse-junction-isolation, then substrate noise isolation is improved, but device complexity and manufacturing complexity increase
Solution Approach 1:
The patent applies local quality by doping only the gate electrode of specific transistors with the opposite polarity from the substrate, rather than requiring comprehensive triple-well isolation for all devices. This localized anti-doping approach provides noise isolation precisely where needed in the voltage reference circuit without mandating complex isolation structures throughout the entire circuit
3Temperature
If the current ratio between flipped-gate and non-flipped-gate transistors is adjusted to achieve ZTC operating point, then temperature independence is improved, but circuit complexity increases
Solution Approach 1:
The patent achieves temperature independence by adjusting the current ratio parameter between the flipped-gate and non-flipped-gate transistors. By changing this electrical parameter (current ratio) rather than fundamentally altering the transistor structure, the circuit achieves ZTC operation with minimal additional complexity
Solution Approach 2:
The patent uses a flipped-gate transistor configuration where the gate and source are swapped compared to a conventional transistor. This inversion of the gate connection creates a transistor whose characteristics complement the non-flipped-gate transistor, enabling temperature compensation through their combined operation
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 provides a temperature-insensitive reference voltage with minimal voltage difference across the entire temperature range, outperforming traditional bandgap reference circuits by eliminating the need for BJTs and reducing power and linearity issues.
Implementation Method 1
the current ratio Iratio of a first current IFGD of a first flipped-gate transistor M1 to a second current INFD of a first non-flipped-gate transistor M2 in a first circuit is adjusted with a plurality of temperatures, to obtain a first current ratio having the same voltage values at the temperatures
Data Source
AI summary
Voltage reference circuits are provided. A voltage reference circuit includes a first transistor, a flipped-gate transistor, a first current mirror unit, a second current mirror unit, and an output note. The first transistor is formed by a plurality of second transistors. A gate and a drain of the flipped-gate transistor are coupled to a gate and a drain of each second transistor. The first current mirror unit is configured to provide a first current to the flipped-gate transistor and a mirroring current in response to a bias current. The second current mirror unit is configured to drain a second current from the first transistor in response to the mirroring current. The output node is coupled to a source of each second transistor and the second current mirror unit, and configured to output a reference voltage. Size of the flipped-gate transistor is less than that of the first transistor.