Cascode Power Amplifier Circuit Without Booster Conversion
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Solution Overview
Problem
Existing power amplifier circuits in mobile communication devices face limitations in maximum output power due to the collector-base withstand voltage of transistors, requiring a booster conversion circuit to increase the power supply voltage, which increases the circuit scale.
Innovation Solution
A power amplifier circuit design incorporating a first and second transistor in a cascode configuration, with a first inductor and capacitor, allowing the power supply voltage to be efficiently distributed and amplified without significantly increasing the circuit scale, enabling increased output power without the need for a booster conversion circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a booster conversion circuit is added to increase the power supply voltage, then the maximum output power is improved, but the device complexity and circuit scale increase
Solution Approach 1:
The power amplifier circuit is divided into two separate transistor stages (first transistor and second transistor), each handling a portion of the voltage amplification. This segmentation allows the circuit to achieve higher output power without requiring a single high-voltage transistor or an external booster conversion circuit, thereby maintaining compact circuit scale while improving maximum output power.
2Power
If the power supply voltage is increased to boost maximum output power, then the power is improved, but the reliability deteriorates due to exceeding collector-base withstand voltage
Solution Approach 1:
The voltage amplification task is segmented across two transistor stages, with each transistor operating within its safe collector-base withstand voltage limits. The first transistor handles initial voltage amplification while the second transistor provides additional gain, ensuring neither transistor exceeds its voltage rating while collectively achieving the desired high output power.
Solution Approach 2:
The first transistor acts as an intermediary stage between the input signal and the second transistor. It provides initial voltage amplification and isolates the second transistor from direct exposure to the full input voltage swing, thereby protecting both transistors from exceeding their collector-base withstand voltage while enabling high output power operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively increases the maximum output power and power-added efficiency by doubling the collector voltage, thereby quadrupling the output power, while maintaining a compact circuit scale, and reducing signal loss in the matching circuit.
Implementation Method 1
An emitter of the second transistor is connected to a collector of the first transistor via the first capacitor
Implementation Method 2
An emitter of the second transistor is grounded via the first inductor
Implementation Method 3
An amplified signal generated by amplifying the radio frequency signal is output from the collector of the second transistor. This design effectively increases the maximum output power and power-added efficiency by doubling the collector voltage, thereby quadrupling the output power
Data Source
AI summary
A power amplifier circuit includes a first transistor, a second transistor, a first bias circuit supplying a first bias current or voltage, a second bias circuit supplying a second bias current or voltage, a first inductor, and a first capacitor. A power supply voltage is supplied to a collector of the first transistor, and an emitter thereof is grounded. A radio frequency signal and the first bias current or voltage are supplied to a base of the first transistor. The power supply voltage is supplied to a collector of the second transistor, and an emitter thereof is connected to the collector of the first transistor via the first capacitor and is grounded via the first inductor. The second bias current or voltage is supplied to a base of the second transistor. An amplified radio frequency signal is output from the collector of the second transistor.