Active Signal Clamp Circuit for Accurate Overrange Limiting

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Solution Overview

Problem

Existing diode-based clamps for protecting electronic circuits against overrange signals are inaccurate due to temperature-dependent threshold voltages, require high-speed voltage references, suffer from leakage, and introduce non-linear capacitances that degrade system linearity.

Innovation Solution

A detector circuit and clamping switch system using a multi-terminal active device, such as PMOSFET, NMOSFET, or BJT, that detects signal levels exceeding thresholds and adjusts impedance to clamp the signal, minimizing distortion and maintaining linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a diode-based clamp is used to limit voltage, then the second circuit is protected against overrange signals, but the threshold voltage shifts with temperature causing inaccuracy

Engineering Contradiction:

Improveprotection accuracyVSAvoidthreshold voltage stability

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent changes the operating parameters of the clamping device by using a voltage-controlled switch instead of a diode, allowing the clamping threshold to be precisely controlled and stabilized through voltage reference circuits rather than relying on temperature-stable diode characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the passive diode-based clamping mechanism with an active voltage-controlled switch system, replacing the reliance on diode threshold characteristics with electronically controllable voltage references and comparison logic

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If a diode-based clamp is used, then voltage limiting is achieved, but high-speed voltage references are required to maintain accuracy

Engineering Contradiction:

Improveclamping threshold accuracyVSAvoidvoltage reference requirements

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The voltage reference circuit serves multiple functions: it establishes the clamping threshold, provides a stable comparison reference for the control logic, and enables precise threshold setting without requiring separate high-speed reference circuits for each function

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If a diode-based clamp is used, then voltage limiting function is provided, but leakage occurs leading up to turn-on affecting distortion

Engineering Contradiction:

Improvesignal path performanceVSAvoidleakage current

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent employs a dynamic switching mechanism where the clamping switch transitions from a high-impedance off state to a low-impedance on state based on real-time signal level detection, eliminating the gradual leakage characteristic of diodes and providing clean, distortion-free signal passage during normal operation

Inventive Principle:

Principle #15Dynamics

4Reliability

If large diodes are used for effective clamping, then voltage limiting capability is improved, but non-linear capacitances are added degrading linearity

Engineering Contradiction:

Improveclamping effectivenessVSAvoidsignal linearity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the electrical characteristics of the clamping element from a large-diode configuration with significant junction capacitance to a voltage-controlled switch with minimal parasitic capacitance, achieving effective clamping while preserving signal linearity through parameter optimization

Inventive Principle:

Principle #35Parameter changes

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 system effectively limits overrange signals with controlled impedance, reducing distortion and maintaining circuit performance, and generates control bits for automatic gain control to optimize signal levels.

Implementation Method 1

the detector circuit comparing the first signal with first and second threshold values and generating a control signal when the detected level of the first signal exceeds the first threshold value or falls below the second threshold value

Methodology Applied

Scientific EffectVoltage comparison:

Implementation Method 2

The control signal controls a state of the clamping switch such that the clamping switch clamps a level of a signal applied to the second circuit when the level of the first signal exceeds the first threshold value

Methodology Applied

Scientific EffectImpedance control:

Data Source

PatentUS10622956B2Signal level detection and overrange signal limiter and clamp for electronic circuits

Publication Date: 2020.04.14 ANALOG DEVICES INC

AI summary

One embodiment is an apparatus including a detector circuit electrically coupled between a signal source and a second circuit, the signal source generating a first signal, the detector circuit detecting a level of the first signal and generating a first control signal when the detected level of the first signal exceeds a first threshold value, and a clamping switch electrically coupled to receive the first control signal from the detector circuit, the clamping switch including a multi-terminal active device. The first control signal controls a state of the clamping switch such that the clamping switch clamps a level of a signal applied to the second circuit when the level of the first signal exceeds the first threshold value.