Transformer-Coupled LNA Output Stage for Low-Noise Differential RF Signals
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Solution Overview
Problem
Current radio frequency (RF) receiver front-end circuits, specifically Low Noise Amplifiers (LNAs), require differential signals for better noise immunity and output swing, but using baluns for conversion results in inherent loss, increasing the noise figure.
Innovation Solution
A semiconductor device with a single-to-differential architecture that utilizes inductors and transformers for transformer coupling to generate differential output signals, enhancing transconductance and improving current efficiency while reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a balun is used to convert single-ended signal to differential signal, then differential output is achieved, but inherent loss increases the noise figure
Solution Approach 1:
The patent extracts and eliminates the balun component from the signal path by implementing a transformer-coupled differential output architecture that directly generates differential signals from the amplifier stage, thereby removing the source of inherent loss and improved noise figure
Solution Approach 2:
The patent merges the signal conversion function into the amplifier stage itself by using transformer coupling at the output, combining the amplification and differential conversion functions into a single integrated stage rather than using separate balun conversion
2Productivity
If transformer coupling is used to generate differential output, then transconductance is enhanced and current efficiency is improved, but device complexity increases
Solution Approach 1:
The transformer-coupled output stage serves multiple functions simultaneously: it provides differential signal generation, impedance transformation, and transconductance enhancement, allowing a single circuit configuration to achieve multiple performance goals without requiring additional separate components
Solution Approach 2:
The patent changes the operating parameters of the amplifier stage by using transformer coupling to achieve higher transconductance and improved current efficiency, optimizing the electrical characteristics of the output stage for better overall performance
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 proposed solution effectively reduces noise and improves signal balance and gain in RF receiver circuits by using transformer-coupled inductors, enhancing transconductance and current efficiency without the loss associated with baluns.
Implementation Method 1
The first inductor and the second inductor are mutually coupled to each other with transformer coupling
Data Source
AI summary
A semiconductor device includes a first transistor, a second transistor, a first inductor and a second inductor. A control terminal of the first transistor is configured to receive an input signal. The second transistor is coupled in series with the first transistor, a first terminal of the second transistor being configured to receive the input signal at a first node. The first inductor is coupled between first transistor and the first node. The second inductor is coupled to a control terminal of the second transistor. The first inductor and the second inductor are mutually coupled to each other with transformer coupling.