Variable-Inductor Amplifier for Parasitic Capacitance Cancellation
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Solution Overview
Problem
Related-art low noise amplifiers (LNAs) face issues with process-variation tolerance and broadband performance due to fixed inductance used to cancel parasitic capacitance, which are affected by semiconductor manufacturing variations.
Innovation Solution
An amplifier design incorporating a variable inductor circuit with adjustable inductance, grounded via a capacitor for DC current interruption, is used to cascade-connect transistors, allowing for optimal cancellation of parasitic capacitance between transistors, thereby improving noise performance across varying process conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed inductance is used to cancel parasitic capacitance, then the circuit structure is simple, but the noise performance is bad due to process variations
Solution Approach 1:
The patent applies the Dynamics principle by replacing the fixed inductance with a variable inductor circuit that can dynamically adjust its inductance value. This allows the inductor to adapt to process variations and optimize noise performance across different manufacturing conditions, directly resolving the contradiction between simple structure and reliable noise performance.
Solution Approach 2:
The patent applies the Parameter changes principle by making the inductance value adjustable rather than fixed. The variable inductor circuit enables changing the inductance parameter to compensate for process variations in parasitic capacitance, thereby improving noise performance without significantly increasing circuit complexity.
2Ease of operation
If a fixed inductance is used to cancel parasitic capacitance, then the inductor value is easy to determine, but the broadband performance is poor
Solution Approach 1:
The variable inductor circuit enables dynamic adjustment of inductance value to maintain optimal noise performance across different frequency bands. This adaptability allows the amplifier to achieve broadband performance while the control mechanism keeps the inductor selection process manageable through automated or semi-automated tuning.
Solution Approach 2:
The variable inductor circuit serves multiple functions: it cancels parasitic capacitance across different frequency ranges, adapts to process variations, and maintains broadband performance. This multi-functionality resolves the contradiction by making a single component adaptable to various operating conditions.
3Ease of manufacture
If an inductor with fixed inductance is used, then the manufacturing process is simple, but process-variation tolerance of noise performance is bad
Solution Approach 1:
The variable inductor circuit introduces adaptability to compensate for process variations. While the manufacturing process becomes slightly more complex, the ability to adjust inductance values allows the system to tolerate manufacturing variations and maintain consistent noise performance across different production batches.
Solution Approach 2:
The variable inductor circuit incorporates feedback mechanisms that allow the system to sense and compensate for process variations. This feedback enables the inductor to self-adjust to maintain optimal noise performance, resolving the contradiction between simple manufacturing and robust process-variation tolerance.
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 amplifier achieves improved noise performance and broadband capabilities by dynamically adjusting the inductance value to compensate for process variations, resulting in enhanced process-variation tolerance and reduced noise figure.
Implementation Method 1
a variable inductor circuit which is electrically connected to the wiring line, has an inductance value that is variable, and is grounded via a capacitor for DC current interruption
Implementation Method 2
the inductance value of the variable inductor circuit is set to an inductance value for canceling a parasitic capacitance between the first transistor and the second transistor
Data Source
AI summary
Provided is an amplifier including: a first transistor connected to a signal input terminal; a second transistor connected to a signal output terminal; a wiring line configured to connect the first transistor and the second transistor to each other; and a variable inductor circuit which is electrically connected to the wiring line, and is grounded via a capacitor for DC current interruption, wherein the inductance value of the variable inductor circuit is set to an inductance value for canceling a parasitic capacitance between the first transistor and the second transistor.