I am currently working on a project, where i need to boost dac output signal from 0..2.5V to 0..10V. I know the general rule on how to do that, but i am in the much dark about the specifics, for ecample what value of my resistors should be while maintaining R2/R1 = 3 ratio; what other components should i add before opamp, maybe some resistors, capacitors etc.
Any insight would be much appreciated.
PS. Scheme shown in the picture below is my base for the needed result, wich I modify in order to find the solution to my problem.

 

Your resistor values are way too low. Try values that are 1000 times or 10000 times larger.

The first question you need to ask is what is resistance of the load?
With a load of 1 Ω you are asking the op amp to deliver 10 A at the output. That is 100 W!
That is not going to happen.

 

Hi Mech
Do you have a datasheet for the 3288RT device.?
The best I can find is this .doc.
E

Update: The first posting of this datasheet was faulty, renewed.

 

Your resistor values are way too low. Try values that are 1000 times or 10000 times larger.

Yes, I get that these values are not realistic, it is only to show the relation of R2 to R1, wich must be 3, so that i get a gain coefficient of 4 and thus boost 2.5V up to 10V.

 

Do you have a datasheet for the 3288RT device.?

I chose this opamp for the time being, I will be looking for one that meets my projects requirements after my project mentor approves of the opamp scheme I am currently working on.

 

The gain is R2/R1 + 1.

 

Yes, and so my R2/R1 ratio must be 3, precisely why I've chosen 3 Ohm for R2 and 1 Ohm for R1 resistors for now.

 

Hi Mech,
It will not work with those values.
E

 

Yes, and so my R2/R1 ratio must be 3, precisely why I've chosen 3 Ohm for R2 and 1 Ohm for R1 resistors for now.

Precisely, not.

3000/1000 + 1 also gives a gain of 4.

I have not indicated the power required to drive R1 + R2 at 10 V. (The answer is 25 W.)

Also, will the op amp work down to 0V input on a single supply?

 

And it goes further... do need to add some output protection? Say 47 ohm resistor connected to output. The feedback resistor can connect after that to compensate for voltage drop

 

Here are some guidelines and a rule of thumb.

Know the input and output impedance of the amplifier and the load. The output impedance of the amplifier should be 10 times lower than that of the load,

For example, suppose your amplifier has to drive a load of 10k Ω resistance. Then the output impedance should be 1 kΩ or less.

 

What will be the actual load on the op amp output?

 

What will be the actual load on the op amp output?

In this case we are looking at a very bad Spice model. There are many bad models in Multisim.

 

Don't believe everything a simulator tells you.

 

The model of this 3288RT operating system is disgusting. It is designed to calculate low-signal analysis. For example, filters. It does not model the load capacity of an operational amplifier well. For some reason, this amplifier is persistently offered in educational institutions. Moreover, Google does not know him.
Here is an example of a circuit calculation showing how the maximum output voltage varies depending on the load value. This is because of the current limitation. I have used a transistor model of an operational amplifier.

 

I am currently working on a project, where i need to boost dac output signal from 0..2.5V to 0..10V. I know the general rule on how to do that, but i am in the much dark about the specifics, for ecample what value of my resistors should be while maintaining R2/R1 = 3 ratio; what other components should i add before opamp, maybe some resistors, capacitors etc.
Any insight would be much appreciated.
PS. Scheme shown in the picture below is my base for the needed result, wich I modify in order to find the solution to my problem.
View attachment 329315

Until the TS can also tell us the current required by the load that needs an input of zero to ten volts there is no way we can provide better than a good guess.
Before we can tell how to "get there" we need to know where to go. Until the requirements are stated adequately there is no way to advise as to the way to meet them.

 

See

 

Visiting post#1 again, I see an apparent error:" boost dac output signal from 0..2.5V to 0..10V. "
I am now assuming that the TS meant "10.0 volts".

It seems that nobody else caught that.

Then, addressing the comment about the LM358 device, it has three important considerations in it's favor.

First, it is commonly available, being produced by several different manufacturers,
Second, it is cheap, being one of the least expensive op-amps in an easy to handle package.
Third, it is more forgiving of poor handling practices and assorted connection errors than many of the much better products available.

In addition, it's various weaknesses can serve to show students that real devices are not the same as the ideal ones used for teaching principles of how circuits work. There is usually a fair distance between theory and actual practice, at least in much of engineering.

 

i need to boost dac output signal from 0..2.5V to 0..10V.

Hi,
What the TS is clearly asking for is how to boost a signal varying from 0v through 2.5V, to an output of 0v through 10.0v.
i need to boost dac output signal

E

 

Hi,
What the TS is clearly asking for is how to boost a signal varying from 0v through 2.5V, to an output of 0v through 10.0v.
i need to boost dac output signal

E

I understand that!! My point was that there was a typo in the first post that was never addressed. Nobody mentioned that point.
And I don't think I saw any response as to what the load properties were.