Translinear Buffer Activity Detection With Common-Mode Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing detector circuits for Media Oriented Systems Transport (MOST) networks consume high current and are unable to effectively reject large common mode signals while detecting small differential signal activity on differential lines.
Innovation Solution
A low-current detector circuit utilizing a translinear buffer configuration with NMOS and PMOS devices, which half-wave rectifies differential input signals and filters them to reject common mode signals, maintaining low impedance at the buffer output and minimizing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diode, filter and comparator configuration is used for detection, then the circuit can detect differential signals, but it consumes more current than ideal and cannot effectively reject common mode signals
Solution Approach 1:
The patent replaces the mechanical/electronic system of diode rectification with a translinear buffer using MOS transistors that provides automatic common mode rejection. The translinear loop configuration creates a balanced differential amplifier that inherently rejects common mode signals while consuming minimal current, eliminating the need for separate filter and comparator stages.
Solution Approach 2:
The translinear buffer performs multiple functions simultaneously: it detects differential signals, rejects common mode signals, and provides low impedance output all within a single circuit configuration. This multi-functionality eliminates the need for separate diode, filter, and comparator components, reducing overall current consumption while maintaining detection precision.
2Measurement precision
If a diode, filter and comparator configuration is used for detection, then the circuit can detect differential signals, but it cannot reject large common mode signals
Solution Approach 1:
The translinear buffer employs asymmetric current paths for differential signals while maintaining symmetric response to common mode signals. The MOS transistor configuration creates different impedance paths for differential versus common mode components, allowing the circuit to amplify differential signals while rejecting common mode interference through the translinear loop's inherent balance.
Solution Approach 2:
The translinear buffer configuration provides automatic feedback mechanisms where the differential amplifier responds to common mode signals by adjusting its operating point, thereby maintaining rejection of common mode interference. The circuit self-regulates to keep the output insensitive to common mode variations while remaining sensitive to differential changes.
3Measurement precision
If high current is consumed by the detector circuit, then better signal detection may be achieved, but power consumption increases
Solution Approach 1:
The patent optimizes the electrical parameters of the MOS transistors in the translinear loop to achieve high detection sensitivity at low current levels. By carefully selecting transistor dimensions, threshold voltages, and bias currents, the circuit maintains excellent signal detection accuracy while consuming minimal power, fundamentally changing the operating parameters from high-current traditional designs to low-current CMOS operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The circuit efficiently detects small differential signals while rejecting common mode signals up to 400MHz and 1V peak-to-peak, reducing power consumption and improving signal detection accuracy in MOST networks.
Implementation Method 1
The differential input signal may be half-wave rectified through the buffer output devices
Implementation Method 2
and may be filtered to provide the detected output
Implementation Method 3
When applying a common mode signal, the buffer's input and output may track each other, and no current may be rectified in the output devices, thus providing excellent common mode rejection
Data Source
Figure 1
Figure 2~4
Figure 5
AI summary
[0045] A low-current differential signal activity detector circuit may be configured to reject large common mode signals on differential input lines, while still detecting smaller differential signals applied to the same set of differential input lines. The detector circuit may comprise a translinear buffer that is driven at the buffer input and at the buffer output by the differential input signals. The differential signal thereby driving the inputs of the detector circuit may be half-wave rectified through the buffer output devices and may be filtered to provide the detected output. When applying a common mode signal, the buffer's input and output may track each other, and no current may be rectified in the output devices, thus providing common-mode signal rejection. The detector circuit may also be configured with two buffers having their outputs coupled to a common node, each buffer input driven by a respective one of the differential input signals. The differential signal thereby driving the inputs of the detector circuit may be fully rectified through the output devices of the two buffers, and may be filtered to provide the detected output. The two buffers may be configured in a symmetrical structure that allows for the rejection of common-mode signals when the outputs of the buffers are coupled to a common node.