Variable Gain Amplifier With Virtual Ground Isolation at Low Voltage
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Solution Overview
Problem
Variable gain amplifiers in radio receivers face a narrow dynamic range when the power supply voltage drops, leading to significant decreases in Signal-to-Noise and Distortion Ratio (SNDR) due to increased distortion and noise when input signal voltages exceed the power supply voltage.
Innovation Solution
A variable gain amplifier design incorporating a plurality of individual amplifiers, an attenuator, and a virtual ground point providing circuit with an isolation active circuit, which maintains high isolation between the signal path and the ground node, allowing for effective attenuation and reduction of distortion and noise, even at low power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power supply voltage is reduced to lower power consumption, then energy efficiency is improved, but the dynamic range narrows and distortion increases when input signal voltages exceed the power supply voltage
Solution Approach 1:
The patent introduces a virtual ground point providing circuit as an intermediary between the attenuator and the actual ground node. This virtual ground point maintains a stable reference potential that is isolated from ground node fluctuations, enabling the attenuator to properly handle large input signals even when the power supply voltage is reduced, thus preventing distortion and maintaining SNDR.
2Use of energy by moving object
If the power supply voltage is reduced, then power consumption decreases, but noise increases relative to the signal level
Solution Approach 1:
The virtual ground point providing circuit acts as an intermediary that stabilizes the reference potential for the attenuator. By isolating the attenuator from ground node fluctuations through the isolation active circuit, the circuit maintains proper signal reference levels even at reduced power supply voltages, preventing noise degradation and maintaining SNDR performance.
3Device complexity
If the ground node is directly connected to the attenuator, then circuit complexity is reduced, but isolation between signal path and ground is insufficient causing distortion and noise mixing
Solution Approach 1:
The patent introduces a virtual ground point providing circuit as an intermediary between the attenuator and the actual ground node. This isolation active circuit provides sufficient galvanic isolation to prevent distortion and noise from the ground node from mixing into the signal path, while still maintaining a practical circuit implementation.
4Reliability
If a virtual ground point providing circuit with isolation active circuit is introduced, then isolation between signal path and ground node is improved, but device complexity increases
Solution Approach 1:
The patent segments the ground reference function by creating a virtual ground point that is electrically isolated from the actual ground node through the isolation active circuit. This segmentation allows the attenuator to have its own independent reference potential, improving signal purity while keeping the added complexity localized to a dedicated isolation stage.
Data Source
AI summary
A variable gain amplifier which includes a plurality of individual amplifiers and variably controls the gain by switching to and using one of the individual amplifier circuits includes an individual amplifier (11) which amplifies a signal input from the input terminal of the variable gain amplifier (100) by an active element (M1), and outputs the input signal, an attenuator (14) which attenuates the input signal by a passive circuit (ZC), and outputs the input signal as an attenuated signal, and a virtual ground point providing circuit (15) which provides a virtual ground potential to the input terminal of the virtual ground point providing circuit (15) by an isolation active circuit (MC) interposed between the input terminal of the virtual ground point providing circuit (15) and the ground node of the variable gain amplifier (100).