Multi-Stage LNA Output Matching Without Gain Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LNAs face challenges in achieving high gain and broadband output matching, particularly at lower power supply voltages like 1.2VDC, leading to reduced RF performance and limited applicability in broadband applications due to narrow frequency range impedance matching.
Innovation Solution
A multi-stage amplifier design incorporating a first stage that receives an input signal and outputs an intermediate signal, with a second stage using a transistor and circuit path to generate an output signal, where the second stage reuses current from the first stage to reduce power consumption and achieve higher gain and broadband impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a capacitive voltage divider (C1 and C2) is used in the output stage to achieve good output matching, then impedance matching is improved, but voltage gain is reduced by 25-50%
Solution Approach 1:
The patent removes the capacitive voltage divider (C1 and C2) from the output stage, extracting the impedance matching function to a separate dedicated circuit. This eliminates the harmful voltage division effect that reduced gain while preserving the necessary impedance transformation through a separate matching network.
Solution Approach 2:
The patent segments the amplifier into distinct functional stages: an input stage, an intermediate stage, and an output stage with separate impedance matching circuitry. This segmentation allows each stage to be optimized independently, with the output stage focused on power delivery and a dedicated matching network handling impedance transformation without compromising gain.
2Ease of operation
If the output stage is tuned with fixed capacitor values (C1 and C2), then proper impedance matching is achieved, but the amplifier is limited to a narrow frequency range
Solution Approach 1:
The patent implements dynamic impedance matching by making the matching network adjustable across different frequency ranges. The output stage can be reconfigured to maintain proper impedance matching at various frequencies, enabling broadband operation rather than being fixed to a single frequency point.
Solution Approach 2:
The amplifier is designed with a universal output stage that can function across multiple frequency ranges. The impedance matching network is configured to provide proper matching for both lower frequency ranges (e.g., 700 MHz-2.6 GHz) and higher frequency ranges (e.g., 1.7 GHz-3.8 GHz), making the amplifier versatile for different application bands.
3Use of energy by stationary object
If conventional amplifier circuits operate at lower power supply voltages (1.2VDC), then power consumption is reduced, but RF performance deteriorates with reduced gain, noise figure, and linearity
Solution Approach 1:
The patent optimizes multiple circuit parameters simultaneously to maintain RF performance at lower voltages: adjusting transistor dimensions (width-to-length ratios), optimizing bias conditions, selecting appropriate device geometries, and tuning impedance matching networks. These parameter changes compensate for the reduced voltage headroom, preserving gain, noise figure, and linearity despite operating at 1.2VDC.
Solution Approach 2:
The patent applies different design optimizations to different parts of the circuit: the input stage uses specific transistor configurations for noise optimization, the intermediate stage is designed for gain with appropriate current biasing, and the output stage is optimized for power efficiency and linearity. Each stage is locally optimized for its specific function while operating at the reduced voltage.
4Device complexity
If the output stage uses a conventional design with voltage divider, then circuit simplicity is maintained, but power efficiency is reduced due to voltage loss
Solution Approach 1:
The patent extracts the voltage division function from the output stage, removing the harmful C1-C2 voltage divider that caused 25-50% gain loss. The output stage is simplified to focus on power delivery, while impedance matching is handled by a separate dedicated network, eliminating the energy loss while maintaining circuit manageability.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A multi-stage device (200-1) includes multiple stages such as a first stage (221-1) and a second stage (222-1). During operation, the first stage (221-1) receives an input signal and outputs an intermediate signal based on the input signal. The second stage (222-1) is coupled to the first stage to receive the intermediate signal and produce an output signal. According to one configuration, the second stage (222-1) includes a transistor (228) and a circuit path between the first stage (221-1) and the transistor (228). The transistor component (228) is controlled to derive the output signal from the intermediate signal inputted to the circuit path.