Cascode Power Amplifier Gain Control Without LDO Regulators
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Solution Overview
Problem
Existing power amplifier modules for mobile communication devices face challenges in controlling signal gain efficiently while maintaining a compact circuit size, often resulting in large circuit sizes due to the use of low dropout (LDO) regulators.
Innovation Solution
The power amplifier module employs a configuration with multiple current sources and transistors in a cascode connection, utilizing level control voltages to manage signal gain without relying on LDO regulators, thereby reducing circuit size and enhancing controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an LDO regulator is used to control the gain of the power amplifier module, then the gain control function is achieved, but the circuit size increases
Solution Approach 1:
The patent extracts the LDO regulator from the circuit and replaces it with a direct voltage control approach. The level control voltage Vramp is directly applied to the bias circuits of the amplifiers without requiring an LDO regulator, thereby eliminating the unnecessary component while maintaining the gain control function.
Solution Approach 2:
The patent introduces bias circuits as intermediary components between the level control voltage Vramp and the amplifiers. These bias circuits convert the voltage control signal into appropriate bias currents for each amplifier stage, enabling gain control without the need for an LDO regulator.
2Power
If three-stage amplifiers are used to amplify the input signal, then the signal amplification is achieved, but the circuit complexity increases
Solution Approach 1:
The patent segments the amplification function into three independent amplifier stages, each with its own bias circuit. This segmentation allows each stage to be controlled independently by the level control voltage Vramp through its dedicated bias circuit, simplifying the overall control architecture despite the multi-stage structure.
Solution Approach 2:
The patent makes the bias circuits universal by designing them with the same structural configuration, where each bias circuit can process the level control voltage Vramp in the same manner. This universality simplifies the design and control of the multi-stage amplifier system, as the same control mechanism applies to all stages.
Data Source
AI summary
A power amplifier module includes a first current source that outputs a first current corresponding to a level control voltage for controlling a signal level of an amplified signal, a second current source that outputs a second current corresponding to the level control voltage, a first transistor in which an input signal and a first bias current are supplied to a base and an emitter is grounded, a second transistor in which an emitter is connected to a collector of the first transistor, the second current is supplied to a base, and a first amplified signal obtained by amplifying the input signal is output from a collector, and a third transistor in which the first current is supplied to a collector, a bias control current or voltage is supplied to a base, and the first bias current is supplied from an emitter to the base of the first transistor.