Power Amplifier Circuit With Segmented Ballast Resistors
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Solution Overview
Problem
Power amplifier circuits in mobile communication equipment face issues with uneven temperature distribution among unit transistors, leading to the current collapse phenomenon, which can be exacerbated by excessive resistance values in emitter ballast resistors, resulting in decreased output power and efficiency.
Innovation Solution
Incorporating both emitter ballast resistors and base ballast resistors in the power amplifier circuit to regulate temperature distribution, with the emitter ballast resistors used under high temperature conditions and base ballast resistors under lower temperature conditions, while maintaining efficient power amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the resistance value of the emitter ballast resistor is increased to restrain uneven temperature distribution, then temperature uniformity is improved, but output power and power added efficiency deteriorate
Solution Approach 1:
The single emitter ballast resistor is segmented into two separate resistors: a emitter ballast resistor connected to the emitter and a base ballast resistor connected to the base. This segmentation allows independent optimization of temperature control and power efficiency functions, resolving the contradiction between temperature uniformity and output power.
Solution Approach 2:
The base ballast resistor acts as an intermediary element that indirectly controls temperature distribution by regulating base current, while the emitter ballast resistor directly controls emitter current. This intermediary approach provides finer temperature control without excessively impacting output power.
2Reliability
If the resistance value of the emitter ballast resistor is increased to prevent current collapse phenomenon, then reliability is improved, but power added efficiency deteriorates
Solution Approach 1:
The temperature control function is segmented between base ballast resistor and emitter ballast resistor, allowing the emitter ballast resistor to use smaller resistance values for preventing current collapse while the base ballast resistor compensates for temperature control, thereby improving power added efficiency.
Solution Approach 2:
The invention changes the resistance parameters of both ballast resistors from a single large resistance value to two smaller resistance values, optimizing the balance between reliability (current collapse prevention) and energy efficiency (power added efficiency).
3Stability of the object's composition
If the resistance value of the emitter ballast resistor is increased to restrain temperature increase, then thermal stability is improved, but output power decreases
Solution Approach 1:
The thermal stability function is segmented between base ballast resistor (primary temperature control) and emitter ballast resistor (current regulation), allowing each resistor to use optimized smaller resistance values that maintain thermal stability without excessively reducing output power.
Solution Approach 2:
The base ballast resistor serves as an intermediary that controls temperature through base current regulation, enabling the emitter ballast resistor to use smaller resistance values that preserve output power while maintaining thermal stability.
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 configuration effectively prevents the current collapse phenomenon, maintains output power, and improves power added efficiency by balancing temperature distribution among transistors without increasing chip area.
Implementation Method 1
a resistive element (hereinafter referred to also as 'the emitter ballast resistor') is inserted between the emitter of each unit transistor and ground to restrain an increase in temperature of each unit transistor
Data Source
AI summary
A power amplifier circuit is capable of restraining uneven temperature distribution among a plurality of unit transistors while restraining the deterioration of the characteristics of the power amplifier circuit. The power amplifier circuit includes: a first transistor group which includes a plurality of unit transistors and which amplifies an input signal and outputs an amplified signal; a bias circuit which supplies a bias current or a bias voltage to a base or a gate of each unit transistor of the first transistor group; a plurality of first resistive elements, each of which is connected between the base or the gate of each unit transistor of the first transistor group and an output of the bias circuit; and a plurality of second resistive elements, each of which is connected between an emitter or a source of each unit transistor of the first transistor group and a reference potential.