Power Amplifier Bias Circuit for Signal Slope Control
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Solution Overview
Problem
Existing power amplification modules for mobile communication devices face challenges in controlling signal gain efficiently, leading to increased circuit size due to the use of Low Drop Out (LDO) regulators, which are cumbersome for large current supply.
Innovation Solution
A power amplification module design that includes an amplification transistor with a constant power supply voltage, a bias current, and a current source that outputs a current corresponding to a level control voltage, along with a bias transistor that adjusts bias currents based on a control voltage, allowing for slope control of transmission signals without the need for an LDO regulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an LDO regulator is used to control the gain of the power amplification module, then the signal level can be controlled, but the circuit scale increases
Solution Approach 1:
The invention extracts the LDO regulator from the power amplification module, separating the voltage regulation function from the amplification function. The LDO regulator is placed outside the module boundary, while only the essential amplification components (amplification transistor, bias transistor, current source) remain inside, thereby reducing the circuit scale of the module while maintaining signal level control capability through the external regulator.
Solution Approach 2:
The bias transistor serves multiple functions: it controls the bias current for the amplification transistor, enables slope control of the transmission signal, and works with the external LDO regulator to achieve gain control. This multi-functionality reduces the need for separate dedicated components, thereby reducing overall circuit scale.
2Power
If an LDO regulator is used to supply large current for gain control, then the power amplification can be achieved, but the circuit becomes cumbersome
Solution Approach 1:
The LDO regulator is extracted from the module and placed externally. The current source within the module generates the required bias current based on control voltage, while the external LDO regulator provides power supply voltage regulation. This separation eliminates the complexity of integrating a large-current-capable LDO regulator within the module while maintaining the necessary power supply and current control functions.
Solution Approach 2:
The current source acts as an intermediary between the control voltage and the amplification transistor. It converts the control voltage into the appropriate bias current, enabling precise control of the amplification stage without requiring the LDO regulator to directly supply large currents to the amplification transistor. This mediation simplifies the internal circuit architecture.
Data Source
AI summary
Provided is a power amplification module that includes: an amplification transistor that has a constant power supply voltage supplied to a collector thereof, a bias current supplied to a base thereof and that amplifies an input signal input to the base thereof and outputs an amplified signal from the collector thereof; a first current source that outputs a first current that corresponds to a level control voltage that is for controlling a signal level of the amplified signal; and a bias transistor that has the first current supplied to a collector thereof, a bias control voltage connected to a base thereof and that outputs the bias current from an emitter thereof.