CMOS Filter Amplifier With Active Load Feedback for UWB Linearity
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Solution Overview
Problem
Current CMOS amplifiers for ultra wideband applications, such as in UWB systems using the MB-OFDM scheme, face challenges in achieving high voltage gain and wideband performance while maintaining linearity, particularly in processing RF signals with high voltage levels and cutoff frequencies.
Innovation Solution
A CMOS amplifier design incorporating an active load circuit with metal-oxide semiconductor field effect transistors (MOSFETs) that feeds back between power sources, a current control circuit receiving common bias, and a signal input circuit, which adds a Zero location and increases gain, allowing for differential signal amplification via MOSFET contact points, thereby enhancing gain-bandwidth product and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a differential amplifier is used for LPF in UWB systems, then the basic amplification function is achieved, but the voltage gain and gain-bandwidth product are insufficient for ultra wideband applications
Solution Approach 1:
The patent implements feedback mechanisms through the active load circuit where MOSFETs feed back between power sources to add Zero location and increase gain. This feedback approach enhances the gain-bandwidth product without requiring a complete redesign of the amplifier structure, thus improving performance while controlling complexity.
Solution Approach 2:
The patent changes key electrical parameters by introducing an active load circuit with MOSFETs that feed back between power sources. This modifies the amplifier's transfer function to add a Zero location and increase gain, directly addressing the insufficient gain-bandwidth product for ultra wideband applications.
2Reliability
If the amplifier structure is simplified, then device complexity is reduced, but linearity and gain performance deteriorate
Solution Approach 1:
The active load circuit employs feedback through MOSFETs connected between power sources to improve linearity. The feedback mechanism linearizes the amplifier's transfer function while the compact MOSFET implementation keeps the additional complexity manageable.
Solution Approach 2:
The patent uses a composite circuit structure combining differential amplifier elements with an active load circuit using MOSFETs. This composite approach integrates multiple functions (amplification, linearity improvement, gain enhancement) into a unified structure that achieves high performance without excessive complexity.
3Power
If conventional CMOS amplifier structures are used, then manufacturing simplicity is maintained, but voltage gain and bandwidth performance are insufficient for ultra wideband applications
Solution Approach 1:
The patent replaces conventional passive load structures with an active load circuit using MOSFETs. This substitution transforms the amplifier's gain characteristics by introducing transconductance-based active loading, which provides higher voltage gain while remaining compatible with standard CMOS fabrication processes.
Solution Approach 2:
The active load circuit with MOSFETs feeding back between power sources changes the electrical parameters of the amplifier by adding a Zero location to the transfer function and increasing gain. This parameter modification achieves ultra wideband performance while using standard CMOS components and fabrication techniques.
Data Source
AI summary
A CMOS amplifier of a filter for an ultra wideband application and a method of the same are provided. In the CMOS amplifier, an active load circuit adds a Zero location and increases a gain by MOSFETs, feeding back operation, and has a property of a high gain and a wide bandwidth. When the CMOS amplifier is applied to a biquad LPF, a high voltage linearity over about 200 mV peak-to-peak and an suitable ultra wideband property over about 320 MHz of an cutoff frequency may be achieved.