# can somebody help me with an exercise?(Opamp)

Discussion in 'Homework Help' started by masterero, Jan 11, 2015.

1. ### masterero Thread Starter New Member

Jan 11, 2015
3
0
Hello,

My name is Marc and I’m from the Netherlands, My teachers gave me this exercise but u don't know the answers. I thought maybe somebody here can help me with it.

I have to simulate this in multisim and get the answers.

In the circuit above you see, besides a resistor and a capacitor, a so called “OpAmp”.

An opamp is an amplifier (operational amplifier) in an IC.

A very popular opamp is the 741 and is used in many applications (projects).

An opamp has 2 inputs (+ and -) and 1 output (referenced to ground).

Without knowing the theory about opamps and the circuit above you will have to build the circuit and simulate it.

What does the circuit do, what is the relation between input and output signal?

On these questions you will try to find answers, using simulation results.

Besides the 3 connections mentioned the opamp has connections to power the IC (see datasheet). These connections are not visible in the circuit above.

For that purpose you will have to use a so called symmetrical power supply (not drawn in the figure above).

A symmetrical power supply contains two DC power sources, one positive and one negative referenced to ground.

Settings of XFG1

Notice: square wave, 1 kHz, 50%, 10 Vp

Settings of XSC1

Notice: Channel A: DC, Channel B: AC.

Simulate the circuit above using the UA741CD as OpAmp.

Try sine, triangle and square.

Questions (will not be assessed):

Can you explain the behaviour of the circuit?

What would be the name of the circuit?

Can you find a link to theory of PEC1 (capacitor and/or inductor)?

Can you find a link to theory of MAT1 (differentiation, integration)?

Exercise 2.

Repeat exercise 1, but let the resistor and the capacitor change places.

Assignment 1.

Combine exercises 1 and 2 using a single IC with 2 OpAmps in it.

Use the UA747CD.

Assignment 2.

Transfer the circuit of assignment 1 to Ultiboard and make a clear PCB design (layout).

Tip for those who want a “good” assessment: before transferring it is wise to add connectors (to wire power and signal lines) to your simulation circuit.

Oct 2, 2009
5,451
1,066
3. ### djsfantasi AAC Fanatic!

Apr 11, 2010
2,907
880
Otherwise, a well prepared post. I assume you've read the link supplied by @MarkML by now, and know we don't have a "Homework Done for You" forum. Please show us what you have done thus far and I hope it will be as detailed as your post. That way, we can provide the best help.

4. ### ScottWang Moderator

Aug 23, 2012
4,933
777
You have to study the RC circuit first and then study the RC circuit in op amp.
RC Integrator circuit
RC integrator circuit op amp

5. ### masterero Thread Starter New Member

Jan 11, 2015
3
0
I'm searching true my books. and i decided for the first question: What does the circuit do, what is the relation between input and output signal? The longer the input is present, the greater the output becomes.

6. ### crutschow Expert

Mar 14, 2008
13,505
3,376
Have you tried the simulation?

7. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,507
512
Like Scott said, it performs integration. You probably already learned how to perform integration in one of your calculus classes, but you have done it on paper. How do you do it in real life? How does your hand held calculator do it? Well, this circuit is how you do it physically. You should have this material in your circuits textbook, I have it in Chapter 7 of my circuits textbook. If you don't, this seem pretty good: http://www.electronics-tutorials.ws/opamp/opamp_6.html