#### N0sterdam

Joined Jul 15, 2012
5
Hello forum, I'm student and i need to do reassessment, i cant fail this module please help with these tasks !!! I have several of them, if you know answer or can help me solve them please write here THANK YOU GUYS !!!

i) Describe how you would construct a circuit using a single capacitor and a single resistor to give a low pass filter with a bandwidth of 5KHz. List the equipment you would need in order to test the circuit. [15 marks]

Show any formulas that you would need and sketch a graph of the expected frequency response for the circuit. [15 marks]

ii) Using the frequency response graph you produce in i) explain how you would measure the performance of the filter including the cut-off frequency, roll-off slope. [5 marks]

iii) Explain how you would use this circuit with another similar circuit to give a band pass filter with a pass-band between frequencies of 1kHz and 5KHz. Sketch a graph of the expected frequency response of this circuit. [20 marks]

iv) The results of an experiment to calculate the output of a filter is as below:

The input voltage is 1v

Frequency
Output (Volts)
20Hz​
0.01​
100Hz​
0.028​
500Hz​
0.124​
800Hz​
0.19​
1KHz​
0.235​
1.2KHz​
0.275​
1.4KHz​
0.315​
1.6KHz​
0.35​
1.8KHz​
0.38​
2KHz​
0.42​
4KHz​
0.66​
8KHz​
0.84​
10Khz​
0.9​
12KHz​
0.92​
15KHz​
0.92​
18KHz​
0.92​
20KHz​
0.92​

Calculate the db gain for each input frequency (2 decimal places). [10 marks]

Draw the frequency response graph and using the graph determine the type of filter, the cut-off frequency, the roll-off slope and determine the component values needed to construct this type of filter. Draw a circuit diagram of the filter. [35 marks]

Again thank you to people who will help

Last edited:

#### WBahn

Joined Mar 31, 2012
25,094
Please show what you have done to attempt to solve these problems and describe where you are running into difficulty.

We are more than willing to help you identify and correct flaws in your understanding or methods; we are not willing to do your work for you.

#### N0sterdam

Joined Jul 15, 2012
5
Ok lets start from the first task. 1.Describe how you would construct a circuit using a single capacitor and a single resistor to give a low pass filter with a bandwidth of 5KHz. List the equipment you would need in order to test the circuit.

I know how the circuit should look like. But i have no idea how its done with low pass filter and that 5KHz, I just dont know where to begin from...
And to test circuit i need to have a amperemeter and voltmeter one of them, and i need tocheck only low pass filter to see if he has that 5KHz.

And formulas to use is frequence(f)= number of wavelength(3x10*8)/ velocity speed(v), and the expected frequency graph of that circuit should look similar to the low pass filter graph it goes down. I'm doing atleast something right. Thx

#### MrChips

Joined Oct 2, 2009
19,923
Ok lets start from the first task. 1.Describe how you would construct a circuit using a single capacitor and a single resistor to give a low pass filter with a bandwidth of 5KHz. List the equipment you would need in order to test the circuit.

I know how the circuit should look like. But i have no idea how its done with low pass filter and that 5KHz, I just dont know where to begin from...
And to test circuit i need to have a amperemeter and voltmeter one of them, and i need tocheck only low pass filter to see if he has that 5KHz.

And formulas to use is frequence(f)= number of wavelength(3x10*8)/ velocity speed(v), and the expected frequency graph of that circuit should look similar to the low pass filter graph it goes down. I'm doing atleast something right. Thx
You are way off track. How much reading and research have you done?
For starters, read this:

http://en.wikipedia.org/wiki/Low-pass_filter

#### N0sterdam

Joined Jul 15, 2012
5
If there is anyone who can help solve these task maybe privite chat on skype or yahoo I for help i will pay some in paypal !!! Please help. Thank you

#### WBahn

Joined Mar 31, 2012
25,094
We are more than willing to help you here, publicly, for free. But you've got to do your part.

While you may find an exception, most of us here are willing to put forth a considerable amount of time to help you learn and, for many of us at least, that time is actually quite valuable. I suspect that many of us have charge-out rates of between $50 and$200 per hour, yet you have several people willing to donate that time to help you learn and we do so gladly. Simply put, it is doubtful you could afford to pay us enough to make it worth our while to simply do your work for you.

Okay, you said that you know what the circuit should look like. Please post a sketch or something showing what that is. Then we can go from there.

#### N0sterdam

Joined Jul 15, 2012
5

But i dont understand what i have to calculate i look true all these helps you gave with given formulas. I dont understand what capacitor omhs are and resistor F. I'm really deperate guys need to finish till 8 o'clock in the morning...

#### Wendy

Joined Mar 24, 2008
21,929
You are going to have to use the resource of this site to display schematics. We support and prefer local hosting, your first attempt did not go well.

How to upload an attachment.

To attach a document or picture to a post

Click "Go Advanced" at the bottom of your post,

One of several options will pop up,

Click "Manage Attachments" much further at the bottom of your post,

To upload a file from your computer click "Browse", then select the file.

Schematics should be .gif or .png format, pictures should be .jpg. .jpg formats will fuzz out schematics, and should not be used for that purpose.

As for your first problem, a hint.

Resistance of R should equal reactance of C at the fold over frequency. It be worth your time to graph this and find out why it is so.

3 db point determines the fold over frequency for filters.

#### WBahn

Joined Mar 31, 2012
25,094
See the attached figure. It has four RC circuit topologies. Which one is the one that you say you know is the correct one?

For that circuit, what if Vout in terms of Vin, R, C, and the frequency?

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