Zin/zout for high-pass filter help?

[xhuang23]

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?

 

[The Electrician]

It would be much easier to help you if you would post a schematic of your filter circuit.

 

[xhuang23]

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.

 

[The Electrician]

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.

 

[rezeew]

I would like to clarify that the expression for Zin and Zout in a high-pass filter circuit depends on the specific circuit design and component values. In general, Zin would equal the impedance of the input source, while Zout would equal the impedance of the output load. However, in a high-pass filter, the impedance seen from the input and output may vary with frequency due to the presence of a capacitor. Therefore, it is important to calculate Zin and Zout at the specific frequency of interest.

In this case, the expression for Zin would be Xc = 1/jwC, as you have correctly identified. This represents the impedance of the capacitor at a given frequency. For Zout, it would depend on the output load. If the output load is purely resistive, then Zout would simply be equal to the resistance value. However, if the output load also contains a capacitor, then the expression for Zout would also involve the impedance of that capacitor.

To determine the exact expression for Zout, you can use the same approach as for Vout/Vin. By writing the output voltage as a function of the input voltage, you can find the equivalent impedance seen from the output. It is important to note that at high frequencies, the capacitor's impedance will decrease, but it will still have an effect on the overall impedance seen from the output.

In summary, the expressions for Zin and Zout in a high-pass filter circuit can vary depending on the specific design and frequency of interest. It is important to carefully consider all components in the circuit and their effects on the impedance seen from the input and output.