Differential Variable Gain Amplifier With Integrated Attenuation
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Solution Overview
Problem
Existing variable gain amplifiers require multiple signal paths and switching circuits, leading to increased size and impedance mismatching issues.
Innovation Solution
A variable gain amplifier design that incorporates a differential amplifier circuit with integrated variable attenuation circuits, allowing resistance value switching based on control signals, eliminating the need for additional switching circuits and reducing impedance mismatching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a power amplifier or attenuator is switchably connected to a high-frequency signal path, then variable gain control is achieved, but the device size increases due to multiple paths
Solution Approach 1:
The patent combines the power amplifier and attenuator into a single integrated high-frequency signal path. The variable gain amplifier includes both amplification and attenuation functions within one compact structure, eliminating the need for separate switchable paths and reducing overall device size while maintaining variable gain control capability.
Solution Approach 2:
The high-frequency signal path is designed to perform multiple functions - both amplification and attenuation - within a single integrated structure. This multi-functional approach allows the device to achieve variable gain control without requiring separate dedicated paths for each function, thereby reducing device size.
2Extent of automation
If a switching circuit including a field-effect transistor is connected in series to the high-frequency signal path, then switching control is achieved, but impedance mismatching occurs and loss increases
Solution Approach 1:
The patent removes the traditional switching circuit including field-effect transistors from the high-frequency signal path. Instead, it uses a reflectionless attenuator structure that provides automatic switching control without requiring series-connected switching devices, thereby eliminating impedance mismatching and associated signal loss.
Solution Approach 2:
The patent introduces a reflectionless attenuator as an intermediary element that enables smooth transitions between different gain states without causing impedance mismatching. This mediator structure allows switching control to be achieved while maintaining impedance matching and minimizing signal loss.
Data Source
Figure 1~2
Figure 3A~3D
Figure 4~6
AI summary
A variable gain amplifier (1) includes a differential amplifier circuit (13) having a pair of input terminals and a pair of output terminals, and a first variable attenuation circuit (14) connected between at least one of the pair of input terminals and the pair of output terminals of the differential amplifier circuit (13) and capable of switching a resistance value on the basis of a control signal which is input from the outside.