# What is the output of the operational amplifier with the input given?

#### Wise Solomon

Joined Apr 24, 2019
3
I am trying to draw out the output of the operational amplifier with the input given below

The first thing I did was calculating the gradient of the slope to give me the slew rate
SR = (change in voltage)/ (change in time) = 0.2/1u = 200kV/sec
This is all I managed to find out.
What is my next step?
What are the expected results?
Thanks, any help and guidance are welcomed

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#### MrSoftware

Joined Oct 29, 2013
1,738
Can you post the schematic, and specify which OpAmp you're referring to? It this a theoretical (homework) question?

#### Wise Solomon

Joined Apr 24, 2019
3
No schematic was given, no op amp was specified, so I assume any opamp will do the job? Yup, its some theoretical question for fun. My "own-paced" homework haha

#### OBW0549

Joined Mar 2, 2015
3,300
No schematic was given, no op amp was specified,

so I assume any opamp will do the job?
WHAT job???? You haven't described any "job," just asked what the response of the op amp will be to the input you gave-- a completely nonsensical question, given the lack of a specific application circuit w/ schematic diagram. With the information given, the best anybody could do is say "the op amp will probably do something."

Yup, its some theoretical question for fun. My "own-paced" homework haha
You need to change your "pace" or you won't learn a darned thing.

#### WBahn

Joined Mar 31, 2012
25,546
I am trying to draw out the output of the operational amplifier with the input given below
View attachment 175745
The first thing I did was calculating the gradient of the slope to give me the slew rate
SR = (change in voltage)/ (change in time) = 0.2/1u = 200kV/sec
This is all I managed to find out.
What is my next step?
What are the expected results?
Thanks, any help and guidance are welcomed
What operational amplifier? What circuit it is in?

#### WBahn

Joined Mar 31, 2012
25,546
No schematic was given, no op amp was specified, so I assume any opamp will do the job? Yup, its some theoretical question for fun. My "own-paced" homework haha
This is like someone asking what will be the response of the car be if the accelerator is pressed from idle to the floor in 100 ms, held there for ten seconds, and then eased off back to idle over 100 ms. Then, when asked what car and what kind of road responding that they assumed any car and any road will give the same result.

#### crutschow

Joined Mar 14, 2008
24,709
An op amp by itself, is a very high-gain differential input amplifier.
Without additional circuitry its only practical use is as a comparator.
For that condition, the op amp output would be a square-wave for your input.

Suggest you do some "own-paced" homework on op amps.

Last edited:

#### MrAl

Joined Jun 17, 2014
7,466
I am trying to draw out the output of the operational amplifier with the input given below
View attachment 175745
The first thing I did was calculating the gradient of the slope to give me the slew rate
SR = (change in voltage)/ (change in time) = 0.2/1u = 200kV/sec
This is all I managed to find out.
What is my next step?
What are the expected results?
Thanks, any help and guidance are welcomed
Hi,

Your next step is to select an op amp and a circuit.
A typical op amp is the LM358, and a typical circuit is an inverting or non inverting amplifier with gain of 1.
However, depending on the choice of op amp, the slew rate of the op amp itself will have to mix with the slope of your input wave at the beginning and end. This might lead to a quadratic (a*t^2) looking wave at the start and end, with some flatness in between.
If you choose to use a low pass filter circuit with the op amp then you will get a smoother output.

So pick an op amp and circuit you'd like to see work with that input and we can go from there.

EDIT: Changed "cubic" to "quadratic" above. During the input slopes the slew rate of the op amp will create a quadratic waveshape either rising or falling.

Last edited:

#### Wise Solomon

Joined Apr 24, 2019
3
Hi all, thanks for the response, yup, its true that it lacks on information and also lacking in learning speed. I'm sorry guys n girls. Anyway, what are the possible ways to delay the input time as shown in diagram above? Thanks

#### WBahn

Joined Mar 31, 2012
25,546
Hi all, thanks for the response, yup, its true that it lacks on information and also lacking in learning speed. I'm sorry guys n girls. Anyway, what are the possible ways to delay the input time as shown in diagram above? Thanks
Apply the input at a later time???...

You really need to be more specific in the questions you are asking.

#### crutschow

Joined Mar 14, 2008
24,709
what are the possible ways to delay the input time as shown in diagram above?
I see no delay.

#### atferrari

Joined Jan 6, 2004
3,914
As I learnt (by posting possible solutions to untold problems that I only knew) it would be better you explain what do you need to implement or solve.

#### MrAl

Joined Jun 17, 2014
7,466
Hi all, thanks for the response, yup, its true that it lacks on information and also lacking in learning speed. I'm sorry guys n girls. Anyway, what are the possible ways to delay the input time as shown in diagram above? Thanks
Hi,

Yes, cut it in half and give half to each input
(from King Solomon)

You dont show any diagram. Are you referring to the original diagram?