Zin/zout for high-pass filter help?

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Discussion Overview

The discussion revolves around determining the input impedance (Zin) and output impedance (Zout) of a high-pass filter circuit with respect to frequency. Participants are exploring the theoretical aspects of impedance in relation to the circuit's transfer function and frequency response.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant proposes that Zin can be expressed as Xc = 1/jwC, but is uncertain about Zout, questioning whether it should be R + Xc or just R.
  • Another participant suggests that Zout will depend on the configuration of the circuit, specifically if the filter is driven by a voltage source with zero internal impedance.
  • There is a request for a schematic of the filter circuit to provide better assistance.
  • A participant mentions that the R value was calculated based on the cutoff frequency of 1.5 kHz.
  • There is a question about how to derive Zin and whether R1 should be considered part of that impedance.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the calculations for Zin and Zout, indicating that there is no consensus on the correct approach or values. Multiple viewpoints on how to calculate these impedances remain present.

Contextual Notes

Participants highlight the importance of circuit configuration and the role of the voltage source's internal impedance in determining Zout. There are also unresolved assumptions regarding the definitions and calculations of Zin and Zout.

Who May Find This Useful

Students and practitioners interested in circuit analysis, particularly in the context of high-pass filters and impedance calculations.

xhuang23
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Homework Statement


An expression for Zin (impedance seen fromthe input) and Zout (impedance seen from the output) of the high-pass filter circuit with respect to frequency is: ?

The Attempt at a Solution


i have, bythe way, equation for transfer function already. Vout/Vin= R/(R+1/jwC). i am pretty sure Zin=Xc=1/jwC but not so sure about zout. would it be R+Xc or just R? i know at high frequency the imaginary part drops, so its just R.

or maybe i am doing this wrong. should i do the same thing for zout/zin as vout/vin?
 
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It would be much easier to help you if you would post a schematic of your filter circuit.
 
JqceA9e.png

it is typical high-pass filter circuit so i didnt think to post a pic. the Vin source was supposed to be 1vpk. the R value i calculated from the fc (cutoff freq) value =1.5kHz.
 
xhuang23 said:

Homework Statement


An expression for Zin (impedance seen fromthe input) and Zout (impedance seen from the output) of the high-pass filter circuit with respect to frequency is: ?

The Attempt at a Solution


i have, bythe way, equation for transfer function already. Vout/Vin= R/(R+1/jwC). i am pretty sure Zin=Xc=1/jwC but not so sure about zout. would it be R+Xc or just R? i know at high frequency the imaginary part drops, so its just R.

or maybe i am doing this wrong. should i do the same thing for zout/zin as vout/vin?

How do you get Zin=Xc=1/jwC? Zin is the impedance calculated at the Vin terminals. Isn't R1 part of that impedance?

Zout will depend on whether or not anything is connected to the Vin terminals. If the filter is driven by a voltage source (having zero ohms internal impedance), then Zout is the impedance seen at the Vout terminals with the Vin terminals shorted (by the impedance of the driving source).

Try calculating Zin and Zout with this information.
 

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