741 op amp ro error?

[djb ecc]

I built a simple 741 op-amp circuit so students could explore the output resistance and maximum output current for various op amps.  The circuit shows that the 741 can deliver more than 5 amps and therefore more than 25 watts.  I am brand new to multisim so I guess I must have something wrong with my circuit. I tried a number of different flavors of 741 but they all work the same in regards to output current.

thanks in advance

[lacy]

I don't see anything wrong in your circut. According to the model information the op-amp in  your circuit is considered an EWB-4 3 terminal Op-amp. I have found these models to not be accurate. If you look in the parts database under where it says "Model manuf./ID" you will find there are more than one model for this op amp. Try selecting the ones that have a 2 or 3 as the last character i.e. ITT/LM741-2.

I believe these to be the most accurate. You can give it a try and see if this is more suitable to your purposes and whether it meets your expectations as far as the output you are looking for.

I hope this helps.

[djb ecc]

Thank You very much Lacy.

I tried every 741, ( I got to get a life, lol) and you hit it right on the nose. The 2 and 3's work.  I will now always look for these op amp flavors and use them in my circuits.  As stated in my first post, I am new to multisim but have built thousands of circuits starting with EWB 2, 3, 4 and 5.  This forum is wonderful, and it's support might be the best feature of multisim.

Thanks again, and you have a great day!

dave

[lacy]

Thank you for your kind words about the forum. We try to help as best we can. If the users of Multisim (like myself) can't find a solution to your problem then one of the very helpful NI Support Staff members usually can.

I must caution you on one thing. I have found that not all op amps have more than one model. There are a few that only have one model and some of the time it is identical to the type that was giving you the problems. In that situation I usually try to find the manufaturer's model information, if it is available,edit it and save it to my user database. I thought I would pass this along to you so the next time you can avoid a potential problem and if you do encounter a problem you will have a way of getting around it.

[djb ecc]

Lacy, your very welcome and thanks for second tip will try it when I become more familiar with multisim.

Thanks again