Variable-Gain Amplifier Circuit With Feedback for Low Noise
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Solution Overview
Problem
Existing high dynamic range, variable gain, low noise amplifier circuits used in beam forming networks face challenges with complex controllers, large integrated circuit die area, and noise figure degradation when adjusting gain, limiting their usability in low gain, low noise modes.
Innovation Solution
The amplifier design incorporates a voltage to current converter, current multiplier, and feedback element to dynamically adjust gain, using a translinear loop and DC correction loop to maintain constant bandwidth and reduce noise figure, while minimizing complexity and power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If passive type interpolation is used for variable gain amplifier, then gain adjustment is achieved, but noise figure degrades immediately as gain is reduced
Solution Approach 1:
The patent employs feedback mechanisms where the output signal is fed back to the input through a feedback network. This feedback loop allows the system to automatically adjust and compensate for noise figure degradation, maintaining optimal performance across the entire gain range including low gain settings where passive interpolation typically fails.
Solution Approach 2:
The invention changes the operating parameters of the amplifier by dynamically adjusting bias currents and voltages based on the desired gain level. By modifying these electrical parameters in real-time, the amplifier can maintain low noise figure even when operating at reduced gain levels, overcoming the limitations of fixed-parameter passive interpolation methods.
2Area of stationary object
If current steering to differential pair is used for variable gain amplifier, then chip area efficiency is improved, but output compression decreases with reduction in gain
Solution Approach 1:
The patent implements dynamic control of the differential pair by using time-varying bias currents and voltages. This dynamic approach allows the amplifier to maintain proper output compression characteristics across all gain levels while still using only one differential pair, thus achieving both area efficiency and performance versatility.
Solution Approach 2:
The invention introduces intermediary control circuits that generate adjusted bias signals based on the desired gain level. These intermediary circuits act as mediators between the control input and the differential pair, ensuring that the differential pair operates optimally at all gain settings without requiring multiple pairs, thereby maintaining both compactness and proper compression characteristics.
3Adaptability or versatility
If adjustable bias is used to increase dynamic range, then dynamic range is improved, but complexity and power requirements increase
Solution Approach 1:
The patent achieves multi-functionality by using a single differential pair to handle all gain levels and dynamic range requirements. The adjustable bias circuit serves multiple purposes: it controls gain, maintains output compression, and extends dynamic range simultaneously. This universal approach eliminates the need for separate circuits for each function, reducing overall complexity despite the enhanced capabilities.
Data Source
AI summary
An amplifier has a voltage to current converter coupled between a first potential and a reference potential and includes a control input coupled to a voltage at an input of the amplifier for converting the voltage at the amplifier input into a corresponding output current. A current multiplier is fed by the output current for producing an increased current. The increased current is fed to a control electrode of a transistor. A feedback element provides the first potential to the voltage to current converter by coupling a voltage produced by the feedback element in response current through the transistor to the voltage to current converter.