# Electronics Forum

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Moderator: pebe

I need urgent help with this stuff. I've been researching a lot yet I couldn't get my head around this circuit. please help me understand it. How the current flows, how the op amp affects the current, how the capacitors, zener diodes etc affect the current.

you can probably tell how much of a beginner i am but thats because the college recruited a teacher whos not even qualified in electronics yet hes my electronics teacher, and he tells me to research about stuff myself rather than him explaining to me how electronic circuits work WITH FULL DETAILS and he says that "if a teacher tells you how e.g. this amplifier works, then your gonna forget it the next day."

please open the image of the circuit in the attachment and help me with these questions:

(TITLE) --> Analyse the effects of changing the values of circuit parameters on the performance of an analogue circuit containing an operational amplifier or transistors

STATE WHAT THE CIRCUIT IS DOING
WHAT HAPPENS WHEN R1 IS CHANGED FROM 100K TO 10K?
WHAT HAPPENS WHEN R2 IS CHANGED FROM 100K TO 10K?
WHAT HAPPENS WHEN C1 IS CHANGED FROM 47Uf to 100Uf?
WHAT HAPPENS WHEN R4 IS CHANGED FROM 100K TO 10K?
WHAT HAPPENS WHEN R3 IS CHANGED FROM 100K TO 10K?
WHAT HAPPENS WHEN R5 IS CHANGED FROM 10K TO 100K?
WHAT HAPPENS WHEN R5 IS CHANGED FROM 10K TO 1K?
WHAT HAPPENS WHEN YOU CHANGE THE FUNCTION GENERATOR VOLTAGE FROM 5V TO 1V?
WHAT HAPPRNS WHEN YOU CHANGE THE OPERATIONAL AMPLIFIER VOLTAGE FROM 9V TO 3V?
Attachments
Untitled.png (20.76 KiB) Viewed 6758 times
اخ سليمان

Posts: 9
Joined: Wed Feb 18, 2015 11:25 pm

A quick look at the circuit should tell you, even with only a basic knowledge of op-amps, that the output will initially go high.

It is not possible to say more than that because no zener voltages are shown. Can you give the values?
pebe

Posts: 1058
Joined: Tue Dec 09, 2003 11:12 pm
Location: Ellon, Scotland

Here are some print screens of the same screenshot of this circuit. I paused the circuit first then took printscreens as the voltages keep changing and the direction of current keeps changing constantly

here it is (attachments)
Attachments
picture 5.png (101.81 KiB) Viewed 6730 times
picture 4.png (98.63 KiB) Viewed 6730 times
picture 3.png (101.67 KiB) Viewed 6730 times
picture 2.png (105.2 KiB) Viewed 6730 times
picture 1.png (72.89 KiB) Viewed 6730 times
اخ سليمان

Posts: 9
Joined: Wed Feb 18, 2015 11:25 pm

some more print screens of the circuit with voltages labelled
Attachments
picture 10.png (96.77 KiB) Viewed 6730 times
picture 9.png (112.1 KiB) Viewed 6730 times
picture 8.png (102.75 KiB) Viewed 6730 times
picture 7.png (102.39 KiB) Viewed 6730 times
picture 6.png (102.85 KiB) Viewed 6730 times
اخ سليمان

Posts: 9
Joined: Wed Feb 18, 2015 11:25 pm

more printscreens of the circuit (there are loads cause i need to label the voltages)
Attachments
picture 13.png (106.41 KiB) Viewed 6730 times
picture 12.png (103.77 KiB) Viewed 6730 times
picture 11.png (106.86 KiB) Viewed 6730 times
اخ سليمان

Posts: 9
Joined: Wed Feb 18, 2015 11:25 pm

more printscreens
Attachments
picture 18.png (109.14 KiB) Viewed 6730 times
picture 17.png (110.65 KiB) Viewed 6730 times
picture 16.png (91.81 KiB) Viewed 6730 times
picture 15.png (110.38 KiB) Viewed 6730 times
picture 14.png (108.93 KiB) Viewed 6730 times
اخ سليمان

Posts: 9
Joined: Wed Feb 18, 2015 11:25 pm

more printscreens (out of 25)
Attachments
picture 23.png (95.84 KiB) Viewed 6730 times
picture 22.png (106.97 KiB) Viewed 6730 times
picture 21.png (108.32 KiB) Viewed 6730 times
picture 20.png (109.09 KiB) Viewed 6730 times
picture 19.png (104.1 KiB) Viewed 6730 times
اخ سليمان

Posts: 9
Joined: Wed Feb 18, 2015 11:25 pm

last 2 printscreens
Attachments
picture 25.png (94.92 KiB) Viewed 6730 times
picture 24.png (105.46 KiB) Viewed 6730 times
اخ سليمان

Posts: 9
Joined: Wed Feb 18, 2015 11:25 pm

D1 and D2 are zener diodes. It was the *zener* voltages that I wanted; they are not shown on the circuit.
pebe

Posts: 1058
Joined: Tue Dec 09, 2003 11:12 pm
Location: Ellon, Scotland

I dont know how to get the zener voltage. Im using circuit wizard and im not an expert on it, I tried properties and I could not find anything relevant, nor could I see the zener breakdown/zener voltage on the circuit when it was being tested. When I clicked on the zener diode in the components list then even over there I could not see the zener voltage written next to it.

please tell me how to find the zener voltage
Attachments
zener diode help.png (34.73 KiB) Viewed 6725 times
اخ سليمان

Posts: 9
Joined: Wed Feb 18, 2015 11:25 pm

From what I can see, Circuity Wizard is a PCB maker and simulator.
So I assume you must have got the circuit from somewhere. The symbol you have used for D1 & D2 is that of a zener diode, not a normal diode (if they are normal diodes then they do nothing and may just have well been left out).

The breakdown voltage of the zener should have been given. If it hasn't, then your questions cannot be answered.
pebe

Posts: 1058
Joined: Tue Dec 09, 2003 11:12 pm
Location: Ellon, Scotland