Determining the type of AC filter.

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Discussion Overview

The discussion revolves around determining the type of AC filter based on the behavior of its components (resistors, capacitors, and inductors) at various frequencies. Participants explore how impedance characteristics influence the classification of filters, including series and parallel resonant circuits.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant outlines the impedance behavior of capacitors and inductors at different frequencies, suggesting that this information can help identify the type of AC filter.
  • Another participant proposes approximating components as shorts or open circuits based on their impedance behavior, indicating that this can assist in analyzing the filter's gain.
  • Some participants express confusion about how to determine which components act as shorts or opens, particularly in relation to the placement of resistors in the circuit.
  • A request is made for equations related to the impedance of resistors, inductors, and capacitors, suggesting that evaluating these at specific frequencies could clarify the analysis process.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on how to determine which components function as shorts or opens, and there is ongoing confusion regarding the implications of component placement in the circuit.

Contextual Notes

There are limitations in the explanations provided, particularly regarding the assumptions made about component behavior and the lack of detailed mathematical derivations for impedance at different frequencies.

Petrucciowns
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By looking at the components in an AC filter how can you determine what type it is based on the following information?
The impedance of a capacitor at very high frequencies is low
The impedance of a capacitor at very low frequencies is high.
Inductors have a direct relationship with frequency
The impedance of an inductor at very high frequencies is high
The impedance of an inductor at very low frequencies is low
The impedance of a resistor stays constant
A series resonant circuit at the resonant frequency is low impedance.
A parallel resonant circuit at the resonant frequency is a High impedance

This has been causing be some problems and I would appreciate some help.
Thank you.
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You can approximate these elements as either shorts or open circuits, depending on how the impedance behaves at high or low frequencies. If you replace them with shorts or opens as appropriate, you can see if the filter produces unity gain or zero gain.
 
How do you know which functions as a short and which as an open? Your explanation was not detailed enough for me to understand. What happens if a resistor is closest to the source?
 
Petrucciowns said:
How do you know which functions as a short and which as an open? Your explanation was not detailed enough for me to understand. What happens if a resistor is closest to the source?

Re-write the equations here that I posted in your other thread for the Z(f) for R, L, C. Then set f=0 to see what the impedance Z is at DC. Then set f=big to see what the impedance Z is at very high frequencies. That should get you going again.
 

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