Linearized Summer Circuit for Differential Kickback Noise Reduction
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Solution Overview
Problem
Conventional receivers experience noise injection due to charge sharing between adjacent circuit nodes in sampler circuitry, leading to signal degradation and improper operation, especially at high data rates.
Innovation Solution
A non-integrating summer circuit with a specific circuit portion that linearizes output impedance across a wide range of output signals, reducing differential 'kickback' noise and improving signal quality for the sampler circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sampler circuitry is used, then the receiver can process signals, but charge sharing between adjacent circuit nodes injects noise into the input nodes, degrading signal quality
Solution Approach 1:
The patent introduces an intermediary summer circuit between the receiver input and the sampler circuitry. This summer circuit acts as a buffer that prevents direct charge sharing between adjacent sampler nodes, thereby eliminating the kickback noise injection into the signal path while still enabling signal processing functionality.
Solution Approach 2:
The patent segments the receiver circuitry into distinct functional blocks: the summer circuit with its own dedicated nodes, and the sampler circuitry with separate nodes. This segmentation isolates the charge sharing effects to local nodes within the sampler block, preventing noise propagation to the summer circuit input nodes through proper circuit topology design.
2Reliability
If the output impedance of the summer circuit varies with output signal level, then the circuit is simpler to implement, but differential kickback noise increases and degrades sampler circuit operation
Solution Approach 1:
The patent employs transistor biasing techniques to maintain relatively constant output impedance across different output signal levels. By carefully selecting bias currents and transistor dimensions, the circuit parameters are optimized to minimize impedance variation, thereby reducing differential kickback noise without requiring complex additional circuitry.
Data Source
AI summary
Some embodiments include apparatuses having a first circuit portion, a second circuit portion, and a third circuit portion. The first circuit portion includes a first transistor to receive a first signal of a differential signal pair and a second transistor to receive a second signal of the differential signal pair. The second circuit portion is coupled to the first and second transistors and a first supply node, the second circuit portion including a first output node and a second output node to provide an output signal pair based on the differential signal pair. The third circuit portion includes a first diode-connected transistor coupled between the first output node and a second supply node and a second diode-connected transistor coupled between the second output node and the second supply node.