YAGEO Group
Webinar Date: September 26, 2024
Basics of RLC Circuits: Looking Deeper than Idealistic Conditions
This post covers Key Takeaways and Frequently Asked Questions from the Yageo Basics of RLC Circuits: Looking Deeper than Idealistic Conditions webinar regarding addressing the nuances when applying RLC circuit principles to real world components such as important component specifications and technologies, parasitic effects of resistors, capacitors, and inductors, designing parasitic effects into a model and how to select components to minimize unwanted component limitations. Whether you’re a seasoned professional or a curious newcomer, you’ll find plenty of valuable information watching the webinar. Links to the Webinar, Resources, and Related Content are provided within the post. A copy of the PowerPoint presentation will be provided for customers that register to watch the recorded webinar. All Snippets and Content Compliments of Yageo.
Key Takeaways
 An RLC circuit consists of a resistor, inductor, & capacitor
 Applications include variable tuned circuits, filters, & oscillators
 The actual capacitor model consists of a series circuit including ideal capacitance, Equivalent Series Resistance (ESR), & Equivalent Series Inductance (ESL)
 The actual resistor model consists of a series circuit of ideal resistance and parasitic inductance with a parasitic capacitance in parallel
 The actual inductor model consists of a parallel circuit including Equivalent Parallel Capacitance (EPC), Equivalent Parallel Resistance (EPR), & parallel inductance, all in parallel to a series circuit Equivalent Series Resistor (ESR)
 Rated capacitance decreases from an increase in DC bias voltage (inversely proportional)
Frequently Asked Questions
Can you explain what an RLC circuit is?
 An RLC circuit is an electrical circuit made up of a Resistor (R), an Inductor (L), and a Capacitor (C). These components control the flow of current and energy in the circuit, often used in tuning circuits to select certain frequencies or output filters.
What does resonance mean in an RLC circuit?
 Resonance in an RLC circuit happens when the inductor and capacitor balance each other at a certain frequency, called the resonant frequency. At this frequency, the circuit allows maximum current to flow.
What is resonance in an RLC circuit?

Resonance occurs in an RLC circuit when the inductive reactance (XL) and capacitive reactance (XC) cancel each other out at a specific frequency, called the resonant frequency (f₀). At this point, the circuit’s impedance is purely resistive, and the current reaches its maximum value in a series RLC circuit. The resonant frequency is given by the formula:
f0= \frac{1}{2\pi\sqrt{LC}}
What are the types of damping in an RLC circuit?
 Damping refers to how the circuit’s oscillations decrease over time. There are three types:
 Overdamped: No oscillations, slow return to normal.
 Critically damped: Fast return to normal without oscillating.
 Underdamped: The circuit oscillates before settling down.
What is the Q factor in an RLC circuit?
 The Q factor measures how sharp or focused the resonance is in an RLC circuit. A higher Q means the circuit is more selective, allowing a narrow range of frequencies to pass.
How does the quality factor (Q factor) affect an RLC circuit?

The Q factor is a measure of how underdamped an RLC circuit is, and it affects the sharpness of the resonance peak. A higher Q factor means a narrower and sharper resonance peak, indicating less energy loss and higher selectivity. It is calculated as:
Q= \frac{1}{R} \sqrt{\frac{L}{C}}

In highQ circuits, energy dissipates more slowly, and the circuit is more selective to a narrow frequency range.
How does impedance change with frequency in a series RLC circuit?
 Impedance (the total resistance to current flow) changes like this:
 At low frequencies, the capacitor causes high impedance.
 At the resonant frequency, impedance is lowest, allowing more current to flow.
 At high frequencies, the inductor increases the impedance.
How does impedance behave in a series RLC circuit at different frequencies?
 In a series RLC circuit:
 At low frequencies, the capacitive reactance (XC) dominates, making the impedance high.
 At the resonant frequency, the inductive and capacitive reactances cancel each other out, leaving only the resistive impedance, which is minimal.
 At high frequencies, the inductive reactance (XL) dominates, increasing the total impedance.
Webinar Links and Resources
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Example Webinar Slides
Much more indepth slides and a copy of the PowerPoint presentation will be provided for customers that register to watch the recorded webinar.