Common-Gate Amplifier Source-Body Resistor for Latch-Up and Frequency Response

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Solution Overview

Problem

CMOS power amplifiers face degradation in frequency responses due to parasitic body capacitance, particularly in common-gate amplifiers, leading to reduced dynamic range and reliability issues.

Innovation Solution

Incorporating a resistor between the source and body terminals of the common-gate amplifier to reduce parasitic body capacitance, thereby improving frequency response and preventing latch-up occurrences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the body terminal of the CG amplifier is shorted to ground with a high voltage supply, then the dynamic range is improved, but reliability deteriorates due to TDDB issues

Engineering Contradiction:

Improvedynamic rangeVSAvoidTDDB reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A resistor is introduced as an intermediary component between the body terminal and ground. This resistor mediates the connection, allowing the body terminal to be effectively grounded for DC biasing while blocking high-frequency parasitic capacitance currents, thus simultaneously achieving good dynamic range and TDDB reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If direct coupling of body terminal and source terminal is used, then TDDB reliability is improved, but frequency response deteriorates due to parasitic body capacitance

Engineering Contradiction:

ImproveTDDB reliabilityVSAvoidfrequency response

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The body terminal connection is changed from a direct low-impedance coupling to a high-impedance connection through a resistor. This parameter change in the body terminal's AC impedance selectively blocks parasitic capacitance currents at high frequencies while maintaining proper DC biasing, thus improving frequency response while preserving TDDB reliability

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If the body terminal is shorted to ground, then body effect is reduced, but parasitic body capacitance increases causing frequency response degradation

Engineering Contradiction:

Improvebody effect reductionVSAvoidfrequency response

Core Design Contradiction:

Ease of operationVSSpeed

Solution Approach 1:

The body terminal connection is made dynamic through the resistor, which presents different impedances at different frequencies. At DC and low frequencies, the resistor allows proper biasing current flow, while at high frequencies, it dynamically blocks parasitic capacitance currents, thus achieving both body effect reduction and good frequency response

Inventive Principle:

Principle #15Dynamics

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

Enhances frequency response and power amplifier efficiency by blocking current leakage through parasitic diodes, reducing body capacitance effects, and preventing latch-up, thus improving operational performance.

Implementation Method 1

parasitic body capacitance from a diode, for example, between a P-Well and the DNW in a p-type substrate or a P-well in an n-type substrate

Methodology Applied

Scientific EffectParasitic capacitance: Parasitic Capacitance

Data Source

PatentUS12381520B2Method and circuit to isolate body capacitance in semiconductor devices

Publication Date: 2025.08.05 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Disclosed is an amplifying circuit and method. In one embodiment, an amplifying circuit, includes: a common-gate (CG) amplifier, wherein the CG amplifier comprises a first transistor, wherein source terminal and body terminal of the first transistor is coupled together through a first resistor.