Pseudo-Differential Active RC Integrator Common-Mode Feedback
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Solution Overview
Problem
Fully-differential active RC integrators suffer from limited output voltage swing and non-linear transconductance, leading to performance hindrances such as noise and distortion, while pseudo-differential active RC integrators offer improved linear transconductance and larger output voltage swing by removing the tail current source and its associated voltage drop.
Innovation Solution
A pseudo-differential active RC integrator with common-mode feedback is designed, featuring two branches with virtual ground nodes and transconductors, along with a common-mode feedback subcircuit to control and stabilize the common-mode output signal, enhancing stability and reducing noise and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fully-differential active RC integrator is used, then differential output signal can be produced, but output voltage swing is limited and non-linear transconductance causes noise and distortion
Solution Approach 1:
The patent removes the tail current source from the fully-differential integrator circuit, converting it to a pseudo-differential configuration. This extraction eliminates the voltage drop across the tail current source that limited the output voltage swing and caused non-linear transconductance, thereby reducing noise and distortion while maintaining differential output capability
Solution Approach 2:
The patent changes the operating parameters by removing the tail current source, which fundamentally alters the voltage swing range and transconductance characteristics of the integrator. This parameter change enables larger output voltage swing and improves linearity, directly addressing the noise and distortion issues
2Object-generated harmful factors
If a pseudo-differential active RC integrator is used, then output voltage swing and linear transconductance are improved, but common-mode output signal stability becomes problematic
Solution Approach 1:
The patent introduces a common-mode feedback subcircuit that monitors the common-mode output signal and adjusts it to maintain stability. This feedback mechanism compensates for the instability inherent in pseudo-differential configurations while preserving the benefits of improved linearity and larger voltage swing
Solution Approach 2:
The common-mode feedback subcircuit acts as an intermediary that mediates between the pseudo-differential integrator stages, controlling and stabilizing the common-mode output signal without interfering with the differential signal processing that provides improved linearity and reduced noise
Data Source
AI summary
A pseudo-differential active RC integrator is described. The pseudo-differential active RC integrator includes a common-mode feedback sub-circuit to control the common-mode output signal of the integrator. The common-mode feedback subcircuit may be coupled to one or more virtual ground nodes of the pseudo-differential active RC integrator, and may include one or more transconductors.