Cascode Power Amplifier Bias Control for Signal Slope
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Solution Overview
Problem
Existing power amplifier modules for mobile communication devices face challenges in controlling signal slope while maintaining circuit size, as conventional LDO regulators lead to increased circuit size due to large current flow.
Innovation Solution
A power amplifier module design incorporating a cascode-connection configuration with current sources and transistors, where the gain is controlled using bias currents and voltages, reducing circuit size and improving signal slope control without relying on LDO regulators.
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 signal level can be adjusted, but the circuit size increases due to large current flow
Solution Approach 1:
The patent changes the control parameter from voltage (VLDO from LDO regulator) to current (IBIAS1, IBIAS2, IBIAS3). By using current sources controlled by voltage-divided signals instead of voltage regulation, the circuit achieves signal level control without requiring large-current LDO regulators, thus reducing circuit size while maintaining control functionality
Solution Approach 2:
The patent extracts the gain control function from the power supply section (LDO regulator) and implements it separately through current sources with voltage dividers. This separation allows the power supply to provide stable voltage without large current flow, while control is achieved through smaller-scaled current control circuits
2Ease of operation
If an LDO regulator is used to control the gain, then slope control can be implemented, but the circuit complexity increases
Solution Approach 1:
The patent segments the gain control into three independent current sources (Ibias1, Ibias2, Ibias3), each controlled by its own voltage divider circuit. This segmentation allows slope control to be implemented by independently adjusting each stage's bias current, achieving complex control functionality through simple, modular circuits rather than a single complex LDO regulator
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.