Phase-Shifted Source Follower Circuitry for Bandwidth and Linearity

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing source follower circuitries face a trade-off between bandwidth and linearity due to high output impedance and signal-dependent modulation, which limits their performance in high-bandwidth communication systems.

Innovation Solution

Incorporating phase shift circuitry into the source follower circuitry to modulate the current source circuitry, thereby reducing signal drop across the input transistor and enhancing linearity, while maintaining or increasing bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If high bandwidth buffers are used as input drivers, then bandwidth is improved, but linearity deteriorates due to larger output impedance and signal dependent modulation

Engineering Contradiction:

ImprovebandwidthVSAvoidlinearity

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The patent introduces a feedback mechanism where the output signal is fed back through phase shift circuitry to the current source. This feedback loop dynamically adjusts the current source to compensate for signal-dependent modulation effects, thereby improving linearity while maintaining the high bandwidth characteristics of the source follower buffer.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent modifies the operating parameters of the current source by applying phase-shifted feedback signals. This changes the effective impedance and modulation characteristics of the current source, reducing signal-dependent modulation and improving linearity without sacrificing bandwidth.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If closed loop buffers are used as input drivers, then linearity is improved, but bandwidth deteriorates

Engineering Contradiction:

ImprovelinearityVSAvoidbandwidth

Core Design Contradiction:

Manufacturing precisionVSSpeed

Solution Approach 1:

The patent segments the buffer functionality into distinct components: the source follower stage for bandwidth and the phase-shifted feedback current source for linearity correction. This segmentation allows each component to optimize its specific function while working together to achieve both high bandwidth and high linearity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates a composite buffer structure combining the source follower topology with phase-shifted feedback current source modulation. This composite approach merges the high bandwidth advantage of source followers with the high linearity advantage of closed-loop buffers, achieving performance benefits of both architectures.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS12237829B2Source follower circuitry including phase shift circuitry

Publication Date: 2025.02.25 XILINX INC

AI summary

An electronic system includes a source follower circuitry that functions as an input driver. The source follower circuitry includes a first input transistor, first current source circuitry, and first phase shift circuitry. The first input transistor includes a first node coupled to a first voltage node, a second node coupled to a first output node, and a gate node coupled to a first input node. The gate node receives a first input signal via the first input node. The first current source circuitry coupled to the first output node and configured to generate a first bias current. The first phase shift circuitry is coupled to the first current source circuitry. The first phase shift circuitry generates a first phase shift signal to modulate the first current source circuitry to reduce signal drop across the first input transistor.