Cross-Coupled Differential Output Stage for Low-Voltage Linearity
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Solution Overview
Problem
Existing differential output stages require high driving signals and have insufficient linearity, leading to gain loss and inefficiencies, especially in satellite receiver applications where low-voltage operation is necessary.
Innovation Solution
A differential output stage with a push-pull output stage topology, featuring cross-coupled connections of voltage buffers and controlled current sources, which compensates for each other to improve linearity and reduce gain loss, eliminating the need for external baluns and allowing for low-voltage operation with high-gain and matched impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional differential output stage is used, then the circuit structure is simple, but the linearity is insufficient and high driving signal is required
Solution Approach 1:
The output stage is segmented into two independent push-pull stages (first and second push-pull output stages), each handling one differential output. This segmentation allows each stage to be optimized independently for linearity while maintaining overall circuit simplicity.
Solution Approach 2:
The patent combines voltage buffer functionality and controlled current source functionality within each push-pull output stage. The first voltage buffer and first controlled current source are integrated in the first push-pull output stage, similarly for the second stage, creating a unified structure that improves linearity without significantly increasing complexity.
2Ease of operation
If a conventional differential output stage is used, then the circuit is easy to implement, but gain loss occurs and energy efficiency is poor
Solution Approach 1:
The patent implements cross-coupling feedback between the two push-pull output stages. The first push-pull output stage is cross-coupled to the second push-pull output stage, and vice versa. This feedback mechanism compensates for gain loss and improves energy efficiency while maintaining ease of implementation through a symmetric structure.
3Adaptability or versatility
If external baluns are used to generate differential signals, then signal conversion is achieved, but cost increases and voltage headroom is reduced
Solution Approach 1:
The patent makes the amplifier circuit self-sufficient by generating differential output signals directly from the push-pull output stages without requiring external baluns. The differential pair amplifies the input signal and naturally produces differential outputs, eliminating the need for additional signal conversion components and reducing both cost and voltage headroom requirements.
Data Source
AI summary
A differential output stage configured for receiving differential input signal comprising first and second signals, comprising a first output for providing a first output signal, and a second output providing a second output signal, the first and second output signals together forming a differential output signal, a first voltage buffer and first controlled current source each connected to the first output, the first voltage buffer being driven by a signal in-phase with the first input signal, the first controlled current source being driven by a signal in-phase with the second input signal, and a second voltage buffer and second controlled current source each connected to the second output, the second voltage buffer being driven by a signal in-phase with the second input signal, the second controlled current source being driven a signal in-phase with by the first input signal.