CMOS Wideband RF Amplifier Buffering for Parasitic Load Compensation
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Solution Overview
Problem
Wideband RF amplifiers suffer from significant performance degradation due to external parasitic elements such as wire-bonds and interface pads, leading to reduced gain and bandwidth, especially at high frequencies.
Innovation Solution
A cascaded connection of a distributed amplifier and a buffer amplifier is implemented, where the buffer amplifier is inserted between the output of the distributed amplifier and the interface packaging elements, comprising cascode stages with resonant networks for DC operating current and RF isolation, to compensate for the high frequency performance degradation caused by parasitics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a distributed amplifier is used to achieve wideband RF amplification, then bandwidth is improved, but performance is severely degraded by external parasitic elements such as wire-bonds and interface pads
Solution Approach 1:
A buffer amplifier stage is inserted between the distributed amplifier output and the external parasitic elements (wire-bonds, interface pads). This intermediary buffer amplifier isolates the distributed amplifier from the harmful parasitic effects, preventing degradation of gain and bandwidth while maintaining the wideband performance benefits of the distributed amplifier architecture.
Solution Approach 2:
The buffer amplifier is designed with preliminary compensation for the expected parasitic effects of wire-bonds and interface pads. By anticipating and counteracting the harmful effects of these parasitic elements before they can degrade performance, the system maintains stable gain and bandwidth across the operating frequency range.
2Device complexity
If conventional amplifier design is used, then circuit simplicity is maintained, but gain-bandwidth product is limited
Solution Approach 1:
The amplifier is divided into two functional segments: a distributed amplifier stage optimized for wideband operation and high gain-bandwidth product, and a buffer amplifier stage optimized for isolation and stability. This segmentation allows each stage to be optimized for its specific function while working together to achieve overall system performance that exceeds conventional single-stage designs.
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 results in a wideband RF amplifier that is robust to external parasitic elements, maintaining a positive gain slope at higher frequencies without parasitics and exhibiting a flat frequency response with enhanced gain and bandwidth when parasitics are present.
Implementation Method 1
comprising cascode stages with resonant networks for DC operating current and RF isolation, to compensate for the high frequency performance degradation caused by parasitics
Data Source
AI summary
The present disclosure relates to an integrated wideband Radio Frequency (RF) amplifier, based on a complementary metal oxide semiconductor (CMOS) technology. In an embodiment the amplifier addresses the shortcomings of conventional wideband amplifiers and is based on a distributed amplifier (DA) topology which typically exhibit severe performance degradation when externally loaded with parasitic circuit elements. In an embodiment of the present invention a buffer amplifier at the output of a conventional DA is able to compensate the impact of parasitic elements. The disclosed circuit can be implemented by fabricating the wideband RF amplifier integrated circuit (IC) on a 130 nm CMOS technology or other comparable CMOS technologies.