OTA Envelope Tracking Amplifier for Low Quiescent Current
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Solution Overview
Problem
Traditional power amplifiers in wireless communication devices are power-hungry due to high quiescent current consumption, especially when implementing wide-bandwidth envelope tracking, which results in significant power loss as heat, especially under peak RF output power conditions.
Innovation Solution
An amplifier circuit design utilizing voltage-to-current conversion to achieve unity feedback and input common-mode rejection, incorporating a voltage-to-current conversion circuit with an operational transconductance amplifier and a current-to-voltage conversion circuit, eliminating the need for input resistors and reducing quiescent current consumption by using a source degenerated amplifier with transconductance boosting and compensation capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a typical linear amplifier is used to achieve wide envelope tracking bandwidth, then the bandwidth is improved, but the quiescent current consumption increases significantly
Solution Approach 1:
The patent changes the operating parameters of the amplifier by using voltage-to-current conversion at the input stage, transforming the input voltage signal into a current signal that directly modulates the OTA. This parameter transformation allows the amplifier to achieve wide bandwidth without requiring high quiescent current, as the current-mode operation is more efficient than traditional voltage-mode operation at wide bandwidths
Solution Approach 2:
The patent substitutes the traditional voltage-mode amplifier architecture with a current-mode architecture using operational transconductance amplifier (OTA). This substitution replaces the conventional voltage amplification mechanism with a current-based transconductance mechanism, which inherently consumes less quiescent current while providing the same bandwidth performance
2Device complexity
If a fixed supply voltage is used in traditional power amplifier, then the circuit complexity is reduced, but the power efficiency deteriorates due to significant power loss as heat
Solution Approach 1:
The patent implements dynamic supply voltage modulation through envelope tracking, where the supply voltage of the power amplifier is modulated dynamically with the envelope of the RF input signal. This dynamic adjustment allows the PA to operate closer to peak level at all times, dramatically improving efficiency by reducing the amount of power dissipated as heat, while the overall circuit complexity remains manageable through the use of standard envelope tracking components
3Use of energy by moving object
If voltage-to-current conversion with OTA is used to reduce quiescent current, then the power efficiency is improved, but the circuit complexity increases due to additional conversion circuits
Solution Approach 1:
The patent merges the voltage-to-current conversion function with the input stage of the amplifier itself, rather than adding a separate conversion circuit. The OTA is configured such that its input terminals receive the voltage signal and its output directly provides the current signal for modulation, combining multiple functions into a single integrated stage that reduces overall circuit complexity while maintaining power efficiency
Data Source
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.