Variable Gain Amplifier Topology for Stable Impedance and Pass Phase
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Solution Overview
Problem
Existing variable gain amplifiers experience variations in pass phase due to changes in gain, primarily because the total number of signal transmitting and shunting transistors being on or off remains constant, leading to fluctuations in impedance.
Innovation Solution
The variable gain amplifier employs a configuration where the total number of input dummies, amplifier circuits, and output dummies is kept constant, with their combinations adjusted based on gain settings, using a gate potential control circuit to manage transistor operations, thereby maintaining output impedance and minimizing phase variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the total number of signal transmitting transistors and signal shunting transistors to be turned on is kept constant, then the impedance from the viewpoint of the amplifying transistor remains constant, but the impedance from the viewpoint of the output terminal changes, causing pass phase variation
Solution Approach 1:
The patent divides the transistor group into multiple sub-groups (first through fourth sub-groups) with different configurations. By selectively turning on specific sub-groups based on gain settings, the patent maintains a constant total number of turned-on transistors while varying their arrangement to compensate for output impedance changes, thereby suppressing pass phase variation.
Solution Approach 2:
The patent dynamically adjusts the configuration of turned-on transistors by selecting different combinations of sub-groups according to gain settings. Although the total number of turned-on transistors remains constant, their spatial arrangement and connection topology change dynamically to maintain optimal impedance characteristics across different gain levels.
2Adaptability or versatility
If the number of signal transmitting transistors is changed to adjust gain, then the gain control range is improved, but the output impedance varies, leading to pass phase errors
Solution Approach 1:
The transistor group is segmented into multiple sub-groups that can be selectively activated. This segmentation enables flexible gain control by turning on different numbers and combinations of sub-groups, while the constant total count of active transistors across all sub-groups maintains impedance stability.
Solution Approach 2:
The patent changes the configuration parameters of the transistor network by selectively enabling different sub-groups rather than simply varying the total number of active transistors. This parameter change approach allows gain adjustment while preserving the constant total transistor count that stabilizes output impedance.
Data Source
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AI summary
A variable gain amplifier includes a first transistor group which is connected to an input terminal and an output terminal, and which amplifies a signal from the input terminal to output the amplified signal to the output terminal; a second transistor group connected to the input terminal; a third transistor group connected to the output terminal; and a control unit configured to control the first transistor group, the second transistor group, and the third transistor group so that a total number of the number of transistors to be turned on in the first transistor group and the second transistor group is kept at a constant value, and total numbers of transistors to be turned on in the first transistor group and in the third transistor group are the same.