I think your simulation software doesn't know that a lousy old LM324 opamp has pretty bad crossover distortion:

thankx and will you tell/sugest which op-amp I use instead of LM324 ?

 

Audioguru,

I can thank National Semiconductor for their model. Do you have a better model?

Isn't that why we take alot of the models with a grain of salt ... and sometimes a big grain.

 

thankx and will you tell/sugest which op-amp I use instead of LM324 ?

There are many newer and better opamps but I don't know if they have accurate simulation models for them.

 

It is better that you tell us the name on some OPAMPS you can get for your project. Then we can decide what is the best for your project.

 

It is better that you tell us the name on some OPAMPS you can get for your project. Then we can decide what is the best for your project.

ok iam posting the another available IC 741 for this.

 

Instrumentation Amplifier with 741

Is this fine or still any problem in this ?

 

The 741 opamp is 42 years old. its performance is poor today.
But it will work fine in your low frequency circuit with low gain.

 

Audioguru ...

That posting you made of the crossover distortion ... what datasheet did that come out of?

That is not mentioned in the March 2000 National Semiconductor datasheet and the three tests in the simulation I did were real close to the published graphs.

 

I did a search on the internet for LM324 and crossover. I found some remarks from audiogurus in several electronics forums. All warning about crossover. Then I was younger I used the LM324 a lot as it was cheap an available, and could be used on DC also. I remember from that time that the Lm324 worked best in DC coupled applications in respect to the output. But I can not say I have seen the figures shown in the pictures posted by this forum audioguru. The datasheet also state

For ac applications, where the load is capacitively coupled to the output of the amplifier, a resistor should be used, from the output of the amplifier to ground to increase the class A bias current and prevent crossover distortion. Where the load is directly coupled, as in dc applications, there is no crossover distortion.

Ok no crossover distortion is perhaps not "the truth, the whole truth, and nothing but the truth" But I do think your scenario Audioguru is not representative for the LM324 then used as described in the datasheet. I will still today recommend the LM324 as an entry point for beginners who want to learn about opamps and do some experimentation. I my self had a lot of fun with that device and learned a lot. And if I burned up some ICs (which I absolutely did) it was no big deal.

 

I don't know where I found the two postings I made of crossover distortion for the LM324 and LM358. Competitor manufacturers comment on the LM324 and LM358 because they were the first "low power" opamps and did not use enough bias current in the output transistors to eliminate crossover distortion. They also have a very poor slew rate and trouble above only 5kHz.

Motorola have the MC33171, MC33172 and MC33174 low power opamps with exactly the same low supply current but no crossover distortion and a slew rate so that frequencies up to 35kHz are fine. They also have a minimum supply of 3V and inputs and outputs that go to ground when there is a single polarity supply.

 

National's LM324 also has a 32V supply rating (+/-16 or 0-32) and a 3V minimum.

 

National's LM324 also has a 32V supply rating (+/-16 or 0-32) and a 3V minimum.

Every other opamp has a max supply of 36V to 44V. The MC331xx that I mentioned in my last post has a max supply of 44V and does everything better than the LM324 and LM358.

 

I agree with the recommendations on using other opamps on projects. The reason the 741 still lives is the reason you don't use it anymore ... it's a good teaching tool. The same applies to the LM324. Granted when doing projects, some will start with those two because they are familiar op amps because of the lab assignments.

I try to remember this is the homework area and those components choosen here are for illustrative and learning purposes.

I'm sure you remember the times when 5% resistors were the common "precision" resistors used in all things except test equipment, although I remember some 1940 designs that I worked on in the 70s with 20% resistors. I certainly wouldn't use 20% resistors these days in any project except a training exercise.

 

Thankx to all of you for helping....

unfortunatily its time to submit my assingment... so i have done it with 741 and also made on veroboard to give final shape.

Thakx again all of you specially joeJester.

 

I HAVE MADE THIS DESIGN WITH ALL OP-AMP ON +12 VOLT D.C. WRT GND. V1 IS VARIABLE FROM 0-100 mili volt wrt to V2.

BUT I AM NOT GETTING RESULT.

PL. ADVISE.

[/QUOTE]

 

Welcome to AAC.

Congratulations, you have practiced the arcane art of necromancy, the revival of a long dead thread. Likely the OP (Original Poster) has solved his problem in the years that has passed, or thrown it away, or something.

Please start your own thread.