Single-Ended Low-Noise Amplifier Without Offset Cancellation Loops
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Solution Overview
Problem
Conventional CMOS LNAs suffer from voltage offsets due to transistor mismatches, leading to increased circuit area, complexity, and power consumption, particularly in RSSI circuits, which implement offset cancellation, resulting in higher power consumption and longer settling times.
Innovation Solution
A low-noise amplifier design using single-ended amplifier stages with integrated band-pass filters and envelope detectors, eliminating the need for offset cancellation loops and operating in the voltage domain with ultra-low power consumption, utilizing a shared architecture for both LNA and RSSI functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offset cancellation loops are implemented in CMOS LNAs, then voltage offset due to transistor mismatches is compensated, but circuit area, complexity, and power consumption increase
Solution Approach 1:
The patent extracts and removes the offset cancellation loop from the LNA circuit, eliminating the source of complexity while accepting that transistor mismatches will cause voltage offsets. This is achieved by using a simple single-ended amplifier architecture without feedback loops for offset cancellation.
Solution Approach 2:
The patent uses a simple resistive divider network instead of complex active offset cancellation circuits. This disposable-like approach uses basic passive components that are cheap and simple, accepting that the transistor mismatches will cause offsets that don't require expensive correction mechanisms.
2Reliability
If offset cancellation loops are implemented in RSSI circuits, then voltage offset due to transistor mismatches is compensated, but power consumption and settling time increase
Solution Approach 1:
The patent removes the power-consuming offset cancellation loop from the RSSI circuit by using a single-ended amplifier architecture. This extraction eliminates the need for complex feedback mechanisms that consume significant power in differential CMOS implementations.
Solution Approach 2:
The single-ended amplifier naturally handles offset issues without requiring additional active compensation mechanisms. The circuit serves itself by using simple passive components and a direct amplification approach that doesn't require power-intensive offset correction loops.
3Reliability
If complex filters are used in LNA design, then signal filtering is improved, but circuit area and complexity increase
Solution Approach 1:
The patent merges the filtering function directly into the amplifier stages by using single-ended amplifiers with inherent frequency selectivity. This combines amplification and filtering in one structure, eliminating the need for separate complex filter circuits.
Solution Approach 2:
The patent uses simple RC time constants and basic passive filtering elements instead of complex active filters. These simple filtering mechanisms provide adequate signal conditioning without requiring large areas for sophisticated filter implementations.
Data Source
AI summary
A low noise amplifier includes a plurality of serially-coupled amplifier stages. Each serially-coupled amplifier stage provides a respective amplified signal, wherein a first amplifier stage receives an input signal, and a last amplifier stage provides an amplified output signal. Each serially-coupled amplifier stage includes a single-ended amplifier having an input, and an output providing the respective amplified signal, a first passive network, and a second passive network. The first passive network has a first terminal forming an input of a respective one of said plurality of serially-coupled amplifier stages, and a second terminal coupled to said input of said single-ended amplifier, the first passive network including a first capacitor coupled in series between the first and said second terminals of the first passive network. The second passive network is coupled in parallel to the single-ended amplifier and between the input and the output of the single-ended amplifier.