Cascode Amplifier Bias for Equal RF Voltage Sharing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power amplifiers face increased power consumption due to the use of impedance conversion matching circuits, which can be mitigated by omitting these circuits and using high voltage transistors, but this requires reducing transistor breakdown voltage, posing design challenges.
Innovation Solution
A power amplifier circuit with a bias circuit that provides DC and RF voltage twice that of the first transistor to the second transistor, configured in a cascode amplifier arrangement, maintaining equal RF and DC voltage drops across both transistors to reduce power consumption and chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an impedance conversion matching circuit is used at the output of the power amplifier, then impedance matching is achieved, but power consumption increases
Solution Approach 1:
The patent removes the impedance conversion matching circuit from the power amplifier output stage, extracting the problematic component that caused increased power consumption. This allows the power amplifier to operate without the additional power consumption associated with impedance conversion circuits while maintaining acceptable performance through direct coupling to the antenna or transmission line.
2Use of energy by moving object
If high voltage supply is used to omit the impedance conversion matching circuit, then power consumption is reduced, but transistor breakdown voltage requirements increase
Solution Approach 1:
The power amplifier output stage is segmented into multiple transistor stages (common emitter stage followed by common base stage) that can operate at lower individual voltage levels. This segmentation allows the overall system to achieve high voltage swing capability without requiring single transistors to withstand high breakdown voltages, thus reducing power consumption while maintaining transistor reliability.
Solution Approach 2:
The patent transitions from a single-transistor high-voltage approach to a multi-transistor cascaded approach, adding a temporal and functional dimension to the voltage generation. By stacking transistors in a cascode configuration, the system achieves high voltage swing through series connection of multiple lower-voltage devices, effectively solving the breakdown voltage problem while maintaining low power consumption.
3Reliability
If the withstand voltage of transistors is reduced, then transistor reliability improves, but the ability to handle high voltage swings decreases
Solution Approach 1:
The voltage swing capability is segmented across multiple transistor stages, each handling a portion of the total voltage range. The common emitter stage handles the initial voltage swing while the common base stage handles the subsequent swing, allowing each transistor to operate within its safe voltage limits while the combined system achieves high overall voltage swing capability.
Solution Approach 2:
The patent introduces intermediate coupling elements (capacitors and inductors) between transistor stages that act as mediators to transfer and transform voltage signals. These intermediaries allow voltage swings to be built up progressively through each stage without exposing individual transistors to excessive voltage stress, thus maintaining both reliability and voltage swing capability.
Data Source
AI summary
A power amplifier circuit includes a first transistor, a second transistor and a bias circuit. The first transistor has a base configured to receive a first signal. The second transistor has an emitter connecting to a collector of the first transistor and a collector configured to output a second signal. The bias circuit is coupled to the first transistor and the second transistor. The bias circuit is configured to provide a direct current (DC) voltage at the collector of the second transistor about twice a DC voltage at the collector of the first transistor. The bias circuit is configured to provide an alternating current (AC) or radio frequency (RF) voltage at the collector of the second transistor about twice an AC or RF voltage at the collector of the first transistor.