Variable Gain Amplifier With Separate Inductive Bandwidth Control
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Solution Overview
Problem
Conventional variable gain amplifiers (VGAs) face inadequacies in achieving optimal linearity and bandwidth, leading to sub-optimal performance in applications such as data communication and automatic gain control, due to parasitic capacitance and bandwidth extension issues.
Innovation Solution
The proposed solution involves a variable gain amplifier design that includes a first switch with a drain terminal coupled to an inductor, and a second switch configured in parallel to the inductor with adjustable resistance in response to a control signal, allowing for improved linearity and bandwidth control through inductor tuning and resistance adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional variable gain amplifier designs are used, then the device can provide basic gain control, but linearity and bandwidth performance are degraded due to parasitic capacitance and bandwidth extension issues
Solution Approach 1:
The amplifier is divided into multiple parallel paths: a first path containing a first switch and first inductor, and a second path containing a second switch and second inductor. This segmentation allows independent control of each path's characteristics, enabling optimization of linearity in one path while managing bandwidth in another, thereby resolving the contradiction between improving linearity and avoiding increased complexity.
Solution Approach 2:
The patent employs dynamically controllable elements including voltage-controlled resistors and adjustable inductors in each path. The resistance values and inductance values can be changed in response to control signals, allowing the amplifier to dynamically adapt its characteristics. This dynamic control enables maintenance of optimal linearity across varying operating conditions without requiring overly complex static circuit designs.
2Speed
If inductors are added to improve bandwidth, then bandwidth is extended, but parasitic capacitance effects worsen linearity
Solution Approach 1:
Different inductor values are assigned to different paths (first inductor in the first path, second inductor in the second path). Each path can be optimized for specific frequency ranges or performance characteristics. This local differentiation allows the system to achieve extended bandwidth through the parallel combination while maintaining linearity by routing signals through appropriately characterized inductor paths, thus resolving the contradiction between bandwidth extension and linearity preservation.
Data Source
AI summary
A variable gain amplifier system includes a variable gain amplifier circuit configured to receive an input signal, apply a gain to the input signal, and generate an output signal in accordance with the gain applied to the input signal. The variable gain amplifier circuit is further configured to receive a gain control signal and a bandwidth control signal. A control module is configured to generate the gain control signal to adjust the gain of the variable gain amplifier circuit and generate, separately from the gain control signal, the bandwidth control signal to adjust a bandwidth of the variable gain amplifier circuit by selectively varying an amount of inductance contributed by an inductor circuit of the variable gain amplifier circuit.