Controllable Gain Amplifier Using Auxiliary Gain Feedback
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Solution Overview
Problem
Conventional amplifier arrangements face challenges in achieving a constant gain slope and linear gain characteristic due to non-linear gain dependence on control signals, which is exacerbated by temperature and process variations, making precise power control difficult in mobile communication systems.
Innovation Solution
An auxiliary amplifier device, similar to the main amplifier, is used to measure the effective gain factor by applying an input signal difference and measuring the output signal difference, allowing for adaptation of the control signal to achieve a desired gain factor, ensuring a constant gain slope across multiple amplifier stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional amplifier arrangements are used to achieve wide output power range, then the output power range is expanded, but the gain characteristic becomes non-linear and dependent on temperature and process variations
Solution Approach 1:
The patent implements a feedback mechanism where the control signal is adjusted based on the measured effective gain factor. The control device modifies the control signal to achieve a desired gain factor, creating a closed-loop system that compensates for non-linearities and variations in the amplifier stages, thereby maintaining linear gain characteristic across wide output power range
Solution Approach 2:
The patent uses an auxiliary amplifier device that is a scaled or substantially similar copy of the main amplifier device. This auxiliary copy is used to measure the effective gain factor without affecting the main amplifier's operation, allowing for accurate characterization and control of the gain characteristic while maintaining the desired output power range
2Productivity
If multiple amplifier stages are used to achieve wide output power range, then the power control capability is improved, but the gain slope becomes non-constant due to variations in individual stages
Solution Approach 1:
The control device continuously adjusts the control signal based on the measured effective gain factor from the auxiliary amplifier. This feedback mechanism compensates for variations in individual amplifier stages, ensuring that the overall gain slope remains constant and predictable across multiple stages, thereby maintaining stable gain characteristic while achieving wide output power range
Solution Approach 2:
The auxiliary amplifier device serves multiple functions: it characterizes the effective gain factor, enables temperature and process variation compensation, and facilitates precise power control. This multi-functional approach allows the system to maintain constant gain slope while providing wide output power range control capability
3Stability of the object's composition
If inductive feedback or degeneration is used to reduce gain characteristic variation, then the gain stability is improved, but the device complexity increases
Solution Approach 1:
Instead of using complex inductive feedback or degeneration circuits, the patent employs a simpler approach by creating an auxiliary copy of the amplifier. This auxiliary amplifier measures the gain characteristic directly, allowing for straightforward feedback control without requiring additional complex circuitry, thereby reducing device complexity while maintaining gain stability
Solution Approach 2:
The auxiliary amplifier device autonomously measures the effective gain factor and provides this information to the control device. This self-service mechanism eliminates the need for complex external control arrangements, allowing the system to maintain stable gain characteristic with minimal additional complexity
Data Source
AI summary
An amplifier arrangement with controllable gain includes a first and a second amplifier device which each have a control input to receive a control signal to adjust a gain factor of the respective amplifier device. A control device is provided which is coupled to the second amplifier device to derive an effective gain factor of the second amplifier device as a function of the control signal. The control device further includes a control output coupled to the respective control inputs of the first and the second amplifier device to provide the control signal depending on a desired gain factor and the effective gain factor.