Product Insights: Non-Ideal Behavior of Passive Components - In Compliance Magazine

Nov 13, 2024

Parasitics refers to undesirable characteristics and unwanted effects that deviate from ideal behavior in electronic components and circuits. These characteristics are often modeled using equivalent lumped elements, which include ResistanceProperty of a conductor due to which it opposes the flow of current through it." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">Resistance, CapacitanceThe ability of a a component or circuit to store an electric charge." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">Capacitance, and Inductancethe ability to store energy in a magnetic field" data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">Inductance.

It is crucial to account for their non-ideal, parasitic characteristics when using passive components to mitigate Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">electromagnetic interference (Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">EMI). You might encounter situations where you initially attempt to employ a component to suppress an unwanted signal, only to discover that it does not yield the expected results. This discrepancy often arises due to the component’s non-ideal behavior.

For instance:

In your exploration of system components for Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">EMI management, understanding how each behaves beyond its self-resonant frequencies is essential. This knowledge ensures that you recognize when a component no longer adheres strictly to its ideal characteristics as a CapacitorA passive electronic component that consists of two conductive plates separated by an insulating dielectric." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">capacitor, inductor, or resistor.

The following outlines the parasitic behavior exhibited by a select few passive components:

Wires

Wires, often underestimated, wield substantial influence over circuit performance. The internal impedance of a long cylindrical conductor—such as a wire—hinges on factors like radius, permittivity, permeability, and conductivity. When scrutinizing these conductors, we observe deviations from ideal models due to material properties and construction techniques. These natural deviations occur beyond the scope of commonly accepted approximations.

At Radio Frequency [RF]Rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">radio frequency (Radio Frequency [RF]Rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">RF) levels, the Skin Effectthe tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor" data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">skin effect becomes significant. High-frequency Alternating Current [AC]A signal or power source that varies with time, switching polarities." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">AC currents predominantly flow on the outer layer (skin) of wires, increasing Alternating Current [AC]A signal or power source that varies with time, switching polarities." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">AC ResistanceProperty of a conductor due to which it opposes the flow of current through it." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">resistance. Remember that this phenomenon also manifests in other components constructed with wires, including inductors, transformers, and common mode chokes.

Transformers

While ideal transformers are a theoretical concept, real-world transformers exhibit parasitic resistances, inductances, and capacitances.

These parasitic elements arise due to the physical construction of transformers and their materials.

Here are some key aspects of the non-ideal behavior of transformers:

Due to their non-ideal characteristics, transformers operate within a restricted BandwidthThe range of frequencies an electronic signal uses on a given transmission medium; the width of a frequency range in the electromagnetic spectrum." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">bandwidth, exhibit insertion loss, adhere to a maximum power rating, and manifest other frequency-, temperature-, and power-dependent behaviors.

Capacitors

No discussion of the non-ideal parasitic behavior of passive components would be comprehensive without acknowledging capacitors. These components play a pivotal role in low-pass filters, the most widely employed FilterAn algorithm or device for removing part(s) of a signal." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">filter type for Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">electromagnetic interference (Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">EMI) mitigation.

Common Mode (CM) Chokes

Another powerful player in Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">EMI suppression is the Common Mode (CM) choke. These chokes find application in mitigating Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">electromagnetic interference (Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">EMI) from switched-mode power supplies (SMPS) and other circuits where CM NoiseA measure of undesired noise mixed into the output." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">noise suppression is essential. By incorporating CM chokes, designers ensure compliance with Electromagnetic Compatibility [EMC]The branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetic energy with reference to the unwanted effects (electromagnetic interference, or EMI) that such energy may induce." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">electromagnetic compatibility standards.

However, there is a caveat: parasitic capacitances associated with CM chokes can detract from their high-frequency filtering performance. If this limitation goes unnoticed, it can lead to extended design cycles and escalated FilterAn algorithm or device for removing part(s) of a signal." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">filter costs. To address this, modeling their non-ideal behavior involves considering parameters like equivalent series inductor (ESL) and equivalent series resistor (ESR)—both stemming from parasitic effects. Understanding these nuances is critical for effective Electromagnetic Interference [EMI]Disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source." data-mobile-support="0" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex="0" role="link">EMI management and optimal system performance.

Other Components Impacted by Parasitic Effects

Resistors:

Inductors:

Summary

This article provides a succinct overview of the non-ideal behavior exhibited by passive components. However, I recommend delving into specialized articles and book chapters that go much deeper into this captivating subject for a more in-depth exploration.

References and Further Reading

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