Current-Mode Amplifier Circuit for Wideband Envelope Tracking

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Solution Overview

Problem

Existing wide-bandwidth envelope tracking designs for power amplifiers in wireless communication devices consume high quiescent current, leading to inefficiency and power loss due to fixed supply voltage and input common-mode issues.

Innovation Solution

An amplifier circuit employing voltage-to-current conversion with unity feedback factor and input common-mode rejection, utilizing a hybrid ETSM architecture with a switching converter and an amplifier circuit that includes a voltage-to-current conversion circuit and a current-to-voltage conversion circuit, along with source degeneration and transconductance boosting techniques, to reduce quiescent current consumption and improve linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a typical linear amplifier is designed to achieve wide envelope tracking bandwidth, then the bandwidth is improved, but the quiescent current consumption increases significantly

Engineering Contradiction:

Improveenvelope tracking bandwidthVSAvoidquiescent current consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent replaces the traditional voltage-mode linear amplifier with a current-mode amplifier architecture. This substitution fundamentally changes the operating principle from voltage control to current control, enabling wide bandwidth operation with reduced quiescent current. The current-mode operation allows the amplifier to respond faster to envelope changes without requiring excessive bias current, directly resolving the contradiction between bandwidth and power consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs dynamic biasing techniques where the amplifier's operating point is adjusted based on the signal conditions. By changing the bias current dynamically rather than maintaining a high fixed quiescent current, the amplifier achieves wide bandwidth when needed while reducing power consumption during low-activity periods. This parameter adjustment strategy directly addresses the bandwidth-power consumption tradeoff.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If a fixed supply voltage is used for the power amplifier, then the circuit simplicity is maintained, but the power efficiency deteriorates due to excessive power dissipation

Engineering Contradiction:

Improvecircuit simplicityVSAvoidpower dissipation

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent introduces dynamic supply voltage modulation through envelope tracking. Instead of using a fixed supply voltage, the amplifier's supply voltage is dynamically adjusted to follow the envelope of the input signal. This dynamic operation allows the amplifier to maintain high efficiency across varying signal conditions by ensuring the supply voltage matches the instantaneous power requirements, thereby reducing power dissipation while maintaining circuit functionality.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements envelope tracking feedback mechanisms where the amplifier's supply voltage is continuously monitored and adjusted based on the input signal envelope. This feedback loop ensures that the supply voltage optimally tracks the signal conditions, maximizing power efficiency. The feedback system automatically adjusts operating parameters to maintain peak efficiency without requiring complex manual intervention, resolving the contradiction between simplicity and efficiency.

Inventive Principle:

Principle #23Feedback

3Loss of energy

If the power amplifier operates at peak RF output power conditions, then the power efficiency is maximized, but the headroom for signal variation is reduced

Engineering Contradiction:

Improvepower efficiencyVSAvoidsignal variation headroom

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent employs dynamic supply voltage adjustment that allows the amplifier to operate at optimal efficiency points while maintaining the ability to handle signal variations. By continuously adapting the supply voltage to match the instantaneous signal envelope, the amplifier can operate near peak efficiency for the current signal level while still having headroom to accommodate future signal variations. This dynamic adaptation resolves the contradiction between operating at peak efficiency and maintaining signal variation headroom.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP3952107B1Amplifier circuit using voltage-to-current conversion to achieve unity feedback factor and input common-mode rejection for linear amplifier and associated envelope tracking supply modulator using the same

Publication Date: 2025.07.02 MEDIATEK INC

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AI summary

An amplifier circuit includes a voltage-to-current conversion circuit and a current-to-voltage conversion circuit. The voltage-to-current conversion circuit generates a current signal according to an input voltage signal, and includes an operational transconductance amplifier (OTA) used to output the current signal at an output port of the OTA. The current-to-voltage conversion circuit generates an output voltage signal according to the current signal, and includes a linear amplifier (LA), wherein an input port of the LA is coupled to the output port of the OTA, and the output voltage signal is derived from an output signal at an output port of the LA.