Gate Resistor Bypass Circuit for Faster FET Switching

Solution Overview

Problem

Integrated circuit devices with larger gate resistors suffer from slow switching times due to the charging of gate-source capacitance through series resistance, which hinders fast switching speed while maintaining RF performance and die area efficiency.

Innovation Solution

A switching circuit design that includes a main FET switch and a bypass switch configured to short the gate resistor during transitions, allowing the bypass switch to close and open at specific states to bypass the gate resistor, thereby reducing switching time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If larger gate resistors are used in FET switches, then linearity and insertion loss are improved, but switching time increases

Engineering Contradiction:

ImprovelinearityVSAvoidswitching time

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The gate resistor is segmented into two functional parts: a main gate resistor (Rg1) that provides the necessary linearity and insertion loss characteristics, and a bypass switch (S1) that can short this resistor during switching transitions. This segmentation allows each part to optimize for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bypass switch introduces dynamic behavior to the gate resistor configuration. During normal operation, the full gate resistor value is present to maintain linearity. During switching transitions, the bypass switch dynamically shorts the resistor to enable fast charging/discharging of gate capacitance, then opens again to restore the linearity benefit.

Inventive Principle:

Principle #15Dynamics

2Strength

If larger gate resistors are used in FET switches, then voltage swing handling is improved, but switching speed decreases

Engineering Contradiction:

Improvevoltage swing handlingVSAvoidswitching speed

Core Design Contradiction:

StrengthVSSpeed

Solution Approach 1:

The gate resistor is segmented into two functional parts: a main gate resistor (Rg1) that provides the necessary linearity and insertion loss characteristics, and a bypass switch (S1) that can short this resistor during switching transitions. This segmentation allows each part to optimize for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bypass switch introduces dynamic behavior to the gate resistor configuration. During normal operation, the full gate resistor value is present to maintain linearity. During switching transitions, the bypass switch dynamically shorts the resistor to enable fast charging/discharging of gate capacitance, then opens again to restore the linearity benefit.

Inventive Principle:

Principle #15Dynamics

3Reliability

If larger gate resistors are used in FET switches, then RF performance at lower frequencies is maintained, but die area increases

Engineering Contradiction:

ImproveRF performanceVSAvoiddie area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The gate resistor is segmented into two functional parts: a main gate resistor (Rg1) that provides the necessary linearity and insertion loss characteristics, and a bypass switch (S1) that can short this resistor during switching transitions. This segmentation allows each part to optimize for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

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

The solution enables faster switching times by decoupling gate resistance from switching speed requirements, allowing the gate resistor to be designed for performance while maintaining fast transitions.

Implementation Method 1

a bypass switch configured to short the gate resistor during transitions

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Implementation Method 2

the gate source equivalent capacitance, Cgs, is being charged by a current flowing through a series resistance Rg

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS10396772B2Methods and devices to improve switching time by bypassing gate resistor

Publication Date: 2019.08.27 PSEMI CORP

AI summary

Implementing a series gate resistor in a switching circuit results in several performance improvements. Few examples are better insertion loss, lower breakdown voltage requirements and a lower frequency corner. These benefits come at the expense of a slower switching time. Methods and devices offering solutions to this problem are described. Using a concept of bypassing the series gate resistor during transition time, a fast switching time can be achieved while the above-mentioned performance improvements are maintained.