Class AB Amplifier With Level Shifting for Lower Power Draw

Solution Overview

Problem

Conventional class AB amplifiers achieve high voltage swing and current drive capability at the expense of high power consumption due to the need for a high source voltage across both voltage and power amplifier stages.

Innovation Solution

A class AB amplifier design that operates the voltage amplifier stage off a first source voltage and includes a level shift stage to adjust the DC level, coupled with a power amplifier stage operating off a second, higher source voltage, allowing both stages to operate efficiently with reduced power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a high source voltage is used in both voltage amplifier stage and power amplifier stage, then high voltage swing and current drive capability are achieved, but power consumption increases

Engineering Contradiction:

Improvevoltage swing and current drive capabilityVSAvoidpower consumption

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The amplifier is divided into two independent stages: voltage amplifier stage operating at low voltage (e.g., 1.8V) and power amplifier stage operating at high voltage (e.g., 5V). Each stage uses its own source voltage, allowing the power amplifier to achieve high voltage swing while the voltage amplifier consumes less power during signal processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A level shift stage is introduced as an intermediary between the low-voltage voltage amplifier stage and the high-voltage power amplifier stage. This level shift stage converts the low-voltage amplified signal to high-voltage level, enabling the power amplifier to operate efficiently at high voltage without requiring the entire amplifier chain to run at high voltage.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If the voltage amplifier stage operates at high source voltage to match the power amplifier stage, then high voltage swing is achieved, but power consumption increases

Engineering Contradiction:

Improvevoltage swingVSAvoidpower consumption

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The amplifier is divided into two independent stages: voltage amplifier stage operating at low voltage (e.g., 1.8V) and power amplifier stage operating at high voltage (e.g., 5V). Each stage uses its own source voltage, allowing the power amplifier to achieve high voltage swing while the voltage amplifier consumes less power during signal processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A level shift stage is introduced as an intermediary between the low-voltage voltage amplifier stage and the high-voltage power amplifier stage. This level shift stage converts the low-voltage amplified signal to high-voltage level, enabling the power amplifier to operate efficiently at high voltage without requiring the entire amplifier chain to run at high voltage.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS7786800B2Class AB amplifier

Publication Date: 2010.08.31 REALTEK SEMICON CORP

AI summary

A class AB amplifier includes: a voltage amplifier stage operating off a first source voltage, and amplifying a differential input voltage to produce a first amplified voltage; a level shift stage coupled to the voltage amplifier stage and adjusting a direct current level of the first amplified voltage to produce a first shift voltage; and a power amplifier stage coupled to the level shift stage, operating off a second source voltage, and converting the first shift voltage to produce a first output current. The second source voltage is larger than the first source voltage.