How Does a Capacitor Introduce Phase Delay in a Circuit?

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SUMMARY

The discussion focuses on measuring phase delay introduced by capacitors in circuits using LTSpice simulations. It emphasizes that phase delay, or phase lag, is best analyzed with sine waves rather than square waves due to the frequency dependence of the delay. The participants clarify that transient analysis is not suitable for observing frequency domain characteristics, recommending a different SPICE analysis mode for accurate results. Understanding the input waveform conditions is crucial for meaningful phase delay measurements.

PREREQUISITES
  • LTSpice simulation software
  • Basic understanding of circuit theory
  • Knowledge of sine wave and square wave characteristics
  • Familiarity with phase delay and phase lag concepts
NEXT STEPS
  • Learn about Bode plots and frequency response analysis
  • Explore LTSpice AC analysis for frequency domain characteristics
  • Study the time constant (tau) in RC circuits
  • Investigate the effects of different waveforms on capacitor charging
USEFUL FOR

Electrical engineers, circuit designers, and students studying capacitor behavior in AC circuits will benefit from this discussion.

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TL;DR
Understanding the phase delay
I simulated the below circuit to capture the phase delay between input voltage and output current in LTSpice
1689755433868.png

How do i measure the phase delay introduced due to capacitor?
1689755562602.png
 

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The rule is that currents in a series circuit are ALWAYS in phase. So I'll ask you what can you conclude from that rule and the circuit you have drawn.
 
When you are using the term "delay" - which signals do you have in mind? Such a delay is the delay between two signals (voltage and/or current) resp. the corresponding phases of these signals,
When you remember your own definitions, you will know what you have to measure/simulate.
 
This would normally be done with sine waves, not square waves. This is because the phase delay depends on the signal frequency. A pulse waveform contains many frequencies. It still can have a phase shift, but it's complicated. So sine waves, which are a single frequency, often swept through a range to make a frequency response (Bode) plot, is what most EEs use.

In any case, you need to specify the conditions, like the input waveform, for phase delay to make sense.
 
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PhysicsTest said:
TL;DR Summary: Understanding the phase delay

I simulated the below circuit to capture the phase delay between input voltage and output current in LTSpice
It looks like you are using a Transient Analysis -- that is not the type of analysis that you should use to see the Frequency Domain characteristics of a circuit. Have a look at this article, and let us know what a better SPICE analysis mode would be... :smile:

https://techweb.rohm.com/know-how/simulation/7916/
 
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I am analyzing the circuit and will come up with the exact problem i am facing.
 
PhysicsTest said:
I am analyzing the circuit and will come up with the exact problem i am facing.

A square wave will charge a capacitor up as soon as it is applied because it is similar to direct current.

Are you wanting to test the time constant, tau, as it is charging?
 
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osilmag said:
A square wave will charge a capacitor up as soon as it is applied
More accurately, a square wave will start to charge up a capacitor with the initial application of the first pulse. Subsequent pulses alternately start to discharge it and recharge it... (see the OP's transient SPICE simulation):

1690549470447.png
 
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Ok
 
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As has been noted the term phase delay (better called phase lag) is defined as the response to a particular frequency sine wave. So your question is not well formulated. Please try again.
 
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