Active-Inductor CTLE for Bandwidth and Nyquist Peaking
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Solution Overview
Problem
Traditional continuous time linear equalizers (CTLEs) face challenges in achieving increased bandwidth and peaking amplitude at Nyquist frequency without excessive power consumption, often requiring passive inductors that occupy large circuit areas.
Innovation Solution
Incorporating an active inductor with an operational amplifier into the CTLE, which implements a transfer function with two zeros and three poles, allowing for improved AC response and increased bandwidth by positioning the poles and zeros effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If passive inductors are used to increase bandwidth and achieve peaking amplitude at Nyquist frequency, then the CTLE can improve signal integrity, but the circuit area occupied increases significantly
Solution Approach 1:
The patent replaces passive inductors (mechanical/electrical components) with an active inductor implemented using transistors and capacitors in a feedback configuration. This substitution eliminates the need for large passive inductor components while achieving the same bandwidth extension and peaking amplitude effects through active circuitry, thereby reducing circuit area occupation.
Solution Approach 2:
The patent changes the fundamental approach from using fixed passive inductor values to using active circuit elements where the inductance is synthesized through transistor parameters (gm, Cgs, Cgd) and feedback resistors. This allows dynamic control and optimization of the inductive effect without being constrained by physical inductor size, enabling bandwidth improvement with reduced area.
2Reliability
If traditional CTLE designs are used to achieve peaking amplitude at Nyquist frequency, then signal integrity can be maintained, but power consumption increases excessively
Solution Approach 1:
The patent substitutes traditional high-power passive inductor-based equalization circuits with an active inductor implementation that uses feedback-controlled transistor circuits. This substitution enables more efficient power utilization while maintaining the necessary peaking amplitude and signal integrity through controlled feedback mechanisms rather than relying on high-power passive components.
Solution Approach 2:
The patent introduces feedback mechanisms in the active inductor circuit where the output is fed back through resistors to control the inductive effect. This feedback allows precise control of the peaking amplitude and bandwidth characteristics while optimizing power consumption, as the feedback loop dynamically adjusts the circuit behavior to achieve the desired signal integrity with minimal power expenditure.
3Speed
If the CTLE bandwidth is increased to handle higher frequency signals, then the peaking amplitude at Nyquist frequency can be maintained, but the circuit complexity increases
Solution Approach 1:
The patent segments the bandwidth extension function into modular active inductor blocks that can be independently designed and optimized. Each active inductor uses a standardized transistor-capacitor-feedback structure, allowing the overall CTLE to achieve increased bandwidth through replication and combination of these modular units rather than through a single complex circuit, thereby managing circuit complexity systematically.
Data Source
AI summary
Various embodiments provide for a continuous time linear equalizer (CTLE) that includes an active inductor, which can be included in a receiver portion of a circuit. For some embodiments, the CTLE in combination with the active inductor can implement a signal transfer function comprising at least two zeros and two poles.