Negative-Capacitance Amplifier Circuit for Parasitic Bandwidth Limits

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Solution Overview

Problem

Current amplifier circuits are limited in bandwidth due to parasitic capacitances, which become more significant as operating frequency increases, and reducing transistor size has diminishing returns on capacitance reduction, limiting the frequencies at which these circuits can operate.

Innovation Solution

The implementation of a digitally-trimmable negative-capacitance capacitor structure, which includes multiple branches and a controller to adjust capacitance values, is used to compensate for the parasitic capacitances in amplifier circuits, effectively extending the bandwidth by connecting negative-capacitance capacitors in parallel with the input, output, and input-output capacitances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If transistor size is reduced to decrease parasitic capacitances, then parasitic capacitances are reduced, but the reduction effect diminishes and manufacturing difficulty increases

Engineering Contradiction:

Improveparasitic capacitancesVSAvoidtransistor size reduction

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent introduces negative capacitance devices as intermediary elements to counteract the parasitic capacitances in the amplifier circuit. These negative capacitance devices act as mediators that cancel out the harmful parasitic effects without requiring further reduction of transistor dimensions, thus resolving the contradiction between reducing parasitic capacitance and maintaining manufacturability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the electrical parameters of the circuit by introducing negative capacitance values that compensate for the parasitic capacitances. By adjusting the negative capacitance parameters to match and cancel the parasitic effects, the circuit achieves extended bandwidth without physical miniaturization, avoiding the diminishing returns and manufacturing challenges of further size reduction.

Inventive Principle:

Principle #35Parameter changes

2Speed

If transistor size is reduced to increase operating frequency, then parasitic capacitances decrease, but the bandwidth extension becomes limited due to diminishing returns

Engineering Contradiction:

Improveoperating frequencyVSAvoidbandwidth extension

Core Design Contradiction:

SpeedVSProductivity

Solution Approach 1:

The patent applies preliminary anti-action by pre-compensating for parasitic capacitance effects before they limit the operating frequency. The negative capacitance devices are configured to counteract the parasitic effects in advance, allowing the amplifier to operate at higher frequencies without being constrained by the diminishing returns of transistor size reduction.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent creates a composite circuit structure that combines conventional amplifier components with negative capacitance devices. This composite approach integrates different functional elements to achieve bandwidth extension that neither conventional transistors alone nor simple size reduction can provide, enabling operation at higher frequencies with sustained productivity.

Inventive Principle:

Principle #40Composite materials

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

This solution allows for the effective compensation of parasitic capacitances, thereby increasing the bandwidth of amplifier circuits and enabling operation at higher frequencies by adjusting capacitance values digitally to match the actual capacitance values of the amplifier components.

Implementation Method 1

The first capacitor is a ferroelectric capacitor with a first negative capacitance

Methodology Applied

Scientific EffectFerroelectric effect:

Implementation Method 2

a first digitally-trimmable negative-capacitance capacitor coupled between the input node of the extended bandwidth amplifier and a power supply terminal. The digitally-trimmable negative-capacitance capacitor includes a first branch, a second branch, and a controller. The first branch includes a first capacitor having a first negative capacitance

Methodology Applied

Scientific EffectNegative capacitance:

Data Source

PatentUS11349440B2Extending bandwidth of analog circuits using ferroelectric negative capacitors

Publication Date: 2022.05.31 APPLE INC

AI summary

Embodiments relate to a circuit implementation for extending the bandwidth of an amplifier. The extended bandwidth amplifier includes an amplifier coupled between an input node and an output node of the extended bandwidth amplifier. The amplifier has an input capacitance and an output capacitance. The extended bandwidth amplifier additionally includes a first digitally-trimmable negative-capacitance capacitor coupled between the input node of the extended bandwidth amplifier and a power supply terminal. The digitally-trimmable negative-capacitance capacitor includes a first branch, a second branch, and a controller. The first branch includes a first capacitor having a first negative capacitance, and a first switch. The second branch includes a second capacitor having a second negative capacitance, and a second switch. The controller is configured to turn on the first switch and the second switch based on the input capacitance of the amplifier.