# Help with this circuit

1. Jun 3, 2010

### sheheryarnoor

Hi everyone i got project from someone

Here is the Project
Code (Text):
www.stanford.edu/class/ee122/Spice_Decks/pspicedemo.pdf
And i did the same what the pdf file tells

Here yall can see the video which i made

Code (Text):
[URL]http://rapidshare.com/files/390247187/CaptureWiz005.wmv
[/URL]

Or

Code (Text):
But rapidhsare one's quality is good

Circuit Pic

The graph which i want to invert

Can someone help me with inverting the graph?
What should i add in the circuit to invert the graph?

Last edited by a moderator: Apr 25, 2017
2. Jun 3, 2010

### dlgoff

Welcome to PF.

The circuit you have is called a http://en.wikipedia.org/wiki/Low-pass_filter" [Broken].

Last edited by a moderator: May 4, 2017
3. Jun 3, 2010

### uart

I think he's probably referring to inverting the amplitude, since it's an "inverting" amplifier topology.

To sheheryarnoor: Just plot the phase response and you'll find it's already "inverted" (as in 180 degrees phase shift in most of the pass band). What you have plotted there is a frequency response "magnitude". The magnitude will always be positive, you need to plot the phase to confirm whether it's "inverting" or not.

4. Jun 3, 2010

### sheheryarnoor

i made a circuit like this
But it gives me error.Isn't it same like high pass filter?i think it is but it is still giving me error
Can anyone make a video tutorial for me please
I need it for my friend he is in the hospital:(

5. Jun 3, 2010

### dlgoff

This is an inverting amp with a gain of A=R2/R1. i.e. Vout=AVin

6. Jun 3, 2010

### sheheryarnoor

can anyone of u make a video tutorial of it for me?
or just draw a circuit even in Paint so i can know how the circuit will look like and what components there will be
Please i wanna help my friend he is in the hospital

7. Jun 3, 2010

### gnurf

You need to connect the positive side of Vin to C1 and the negative input to ground -- right now you've got the negative side of Vin connected to C1 and an open circuit on the positive side. And also remove the voltage source on the output, and put your probe here.

8. Jun 4, 2010

### sheheryarnoor

i removed voltage source and connected as u said

But the graph shows like this then

9. Jun 4, 2010

### gnurf

When I said "the positive side" I meant the terminal that has a "+" sign next to it. The negative side has a "-" sign next to it. I'm not sure what you're trying to do anymore, but in your last attached picture (which I guess is supposed to be an "integrator"):

1) Connect the positive output of Vin (marked with a + sign) to the 1k resistor and the negative side to ground.

2) Connect the negative input of the opamp to the node where the resistors and capacitor meet, and the positive input of the opamp to ground.

If your input signal is a square pulse train, what do you expect to get on the output?

10. Jun 4, 2010

### sheheryarnoor

See the red lines i want graph like those red lines the red lines have been sketched in Paint to give me a clue that what graph will look like
Can u make like these?
Actually i am not a student of Electronics i am doing it for my friend he is in the hospital so i wanna help him

Last edited: Jun 4, 2010
11. Jun 4, 2010

### dlgoff

Oops. Actually it is a high pass filter. I didn't see the capacitor at first. Sorry. The corner frequency = 1/2πR1C1 with a bandpass gain of R2/R1.

12. Jun 5, 2010

### sheheryarnoor

lol as i told u am not a student of electronics just helping my friend
So i dont know what are u talking abt?:p
Can u make a graph like the red line?

13. Jun 5, 2010

### vk6kro

You can combine low pass and high pass filters to get passbands like that one.

[PLAIN]http://dl.dropbox.com/u/4222062/low%20pass%20high%20pass.PNG [Broken]

Here R2 and C1 form a low pass filter to produce the slope from 10 KHz upwards and
C2 and R1 form a high pass filter to produce the slope from 1 KHz downwards.

Last edited by a moderator: May 4, 2017
14. Jun 6, 2010

### sheheryarnoor

what is this triangle thing which u have used?
GND Analog?or what?

15. Jun 6, 2010

### sheheryarnoor

"vk6kro" Can u make a video of it?I tried to make a circuit like u have shown but mine graph was change it wasn't like urs
So i wish u make a video of it

16. Jun 6, 2010

### vk6kro

The triangle is a ground symbol.

Not sure what sort of video you mean. Why would you do that?

Are you plotting with LT Spice 4?

17. Jun 6, 2010

### uart

"My friend's in hospital and the only thing that will cure him is a video of the simulation of a band-pass filter"

Man you've gotta give this guy the award for most creative excuse of why someone else should do my homework/assignment for me. :rofl:

18. Jun 6, 2010

### vk6kro

Hopefully his friend will have a speedy recovery and be able to do his own homework. :)

I'm sure we all wish him well.

19. Jun 7, 2010

### sheheryarnoor

i mean get a screen recorder and when u make a circuit record it and then upload it to utube so i can see what did u do and what did i do wrong

20. Jun 7, 2010

### sheheryarnoor

i mean make a circuit and graph like u have showed in ur pics
While making them make a video of it
Record ur screen by screen recorder so i can know what did i do wrong?