Variable Gain Amplifier Bias Segmentation for Stable Phase Linearity
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Solution Overview
Problem
Existing variable gain amplifiers (VGAs) face challenges in maintaining constant output phase and linearity across different gain states, particularly with the advent of 5G technology, where phase stability and high linearity are crucial, especially as frequency increases.
Innovation Solution
The proposed solution involves a variable gain amplifier circuit structure with multiple parallel transistors in each amplifying circuit, allowing independent bias control and the use of degeneration circuits to improve linearity, ensuring consistent dynamic gain curves and phase stability across varying gain states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a current steering variable gain amplifier structure is used to control VGA gain, then gain control is effective, but output phase changes continuously with amplifier gain
Solution Approach 1:
The patent divides the amplifying circuit into multiple parallel amplifying sub-circuits, each with independent bias control. This segmentation allows the total gain to be controlled by adjusting the bias of individual sub-circuits while maintaining a consistent output phase reference, thereby resolving the contradiction between effective gain control and phase stability.
2Ease of operation
If a bias-controlled variable gain amplifier structure is used to control VGA gain, then gain control is effective, but output phase changes with bias current
Solution Approach 1:
The patent segments the amplifying circuit into multiple parallel sub-circuits with independent bias control, allowing gain adjustment through bias manipulation while maintaining phase stability. Additionally, the use of degeneration circuits provides a stabilizing mechanism that counteracts phase variations caused by bias current changes.
Solution Approach 2:
The patent employs degeneration circuits that modify the bias conditions of the transistors in a controlled manner. By changing the degeneration parameters (such as adding resistive or reactive elements in series with transistor terminals), the circuit achieves gain control while maintaining constant output phase across different bias current levels.
3Stability of the object's composition
If phase compensation network is added to input stage of variable gain amplifier, then output phase is kept constant, but linearity deteriorates as gain is switched
Solution Approach 1:
Instead of using a phase compensation network that degrades linearity, the patent segments the amplifying circuit into multiple parallel sub-circuits. Each sub-circuit contributes to the total gain while maintaining inherent phase stability, thus achieving constant output phase without compromising linearity during gain switching.
Solution Approach 2:
The patent uses degeneration circuits to dynamically adjust bias parameters in a controlled manner, achieving phase stability through parameter optimization rather than through compensation networks. This approach maintains better linearity by avoiding the additional complexity and non-linearities introduced by separate compensation circuits.
4Speed
If frequency increases for 5G technology applications, then communication capability is enhanced, but linearity deterioration becomes more serious
Solution Approach 1:
The patent employs degeneration circuits that optimize bias parameters dynamically, improving linearity performance at higher frequencies. By adjusting the degeneration parameters (such as adding inductive or capacitive elements), the circuit compensates for frequency-dependent non-linearities, thereby maintaining good linearity even at 5G operating frequencies.
Solution Approach 2:
The segmented architecture with multiple parallel amplifying sub-circuits allows each sub-circuit to operate at optimized bias conditions, improving overall linearity at high frequencies. This segmentation reduces the burden on individual transistors and allows for better control of non-linear effects at 5G frequency ranges.
Data Source
AI summary
A variable gain amplifier and an electronic apparatus. The variable gain amplifier includes a first transconductance stage circuit and a second transconductance stage circuit, where the first transconductance stage circuit includes a first amplifying circuit and a second amplifying circuit, the second transconductance stage circuit includes a third amplifying circuit and a fourth amplifying circuit, the first amplifying circuit and the fourth amplifying circuit form a differential input pair, and the second amplifying circuit and the third amplifying circuit form a differential input pair, and where each amplifying circuit of the first amplifying circuit, the second amplifying circuit, the third amplifying circuit, and the fourth amplifying circuit includes a plurality of parallel transistors, and bias control of the plurality of transistors is independent of each other.