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h.z
11-27-2010, 03:26 PM
Can op amp LM741 work with 9V supply voltage?

bertus
11-27-2010, 03:45 PM
Hello,

In the datasheet is stated 5 Volts supply.
This means taht 9 Volts is to low.
Also there is stated that the LM741 is an obsolete component.

Bertus

beenthere
11-27-2010, 04:42 PM
In the datasheet is stated 5 Volts supply.Dropped a place. That is +/-15 volts in the data sheet.

What do you want to do? There are a huge number of better op amps, and many that are designed to operate with a single supply.

Audioguru
11-27-2010, 05:24 PM
The 741 opamp is 42 years old.

The written spec's are only with a plus and minus 15V supply but the "typical" graphs all show a supply as low as plus and minus 5V. With a supply as low as only plus and minus 5V then the typical output swing is shown to be almost nothing.

h.z
11-28-2010, 12:28 AM
i asked just because I'm curious. 9V battery is easy to get, that's why I was wondering if the op amp could work with 9V supply voltage. as far as i know, op amp can amplify the input voltage to maximum the supply voltage. right?

so, audioguru op amp LM741 could work with 9V supply voltage?

thatoneguy
11-28-2010, 12:54 AM
You can use two 9V batteries to supply it, connect negative to positive, call that point "ground", for a dual supply.

That is sub-optimal, I'd suggest going with a more modern op amp.

Audioguru
11-28-2010, 12:58 AM
You can use two 9V batteries to supply it, connect negative to negative, call that point "ground", for a dual supply.

"Negative to negative" does not make a dual-polarity supply.
It makes two positive supplies which are not useful.

Bill_Marsden
11-28-2010, 01:02 AM
You could also use something like a LM324, which is 4 in one package. That chip is rated from 3V to 30V, which similar specs to a LM741. Both are available at Radio Shack.

The LM741 is extremely old, which translates into very poor specs compared to more modern types.

Creating a Virtual Power Supply Ground (http://forum.allaboutcircuits.com/showthread.php?p=84026#post84026)

h.z
11-28-2010, 01:34 AM
You could also use something like a LM324, which is 4 in one package. That chip is rated from 3V to 30V, which similar specs to a LM741. Both are available at Radio Shack.




Minimum supply voltage is 3V? that is very low. so, you're saying i could use 9V supply voltage for LM741?

retched
11-28-2010, 01:41 AM
No, you cant use one 9v battery with a 741.

Take 2 9v batteries connect them in series.

Take the '+' on battery 'A' and connect it to the '-' on battery 'B'

The wire that connects the two batteries can now be your GROUND.

The '+' on battery 'B' is now +9v Hook that to the positive supply pin on the 741
The '-' on battery 'A' is now -9v Hook that to the negative supply pin on the 741

That will allow you to work with a LM741.

If you are just trying to learn theory, then thats fine, but If you are trying to make a project to keep and use, you can, and should, find better OPAmps.

Audioguru
11-28-2010, 01:51 AM
so, audioguru op amp LM741 could work with 9V supply voltage?
Simply read the datasheet.
The written spec's guarantee operation only when the supply is a total of 30V.
The graphs show very poor performance for "typical" devices at low voltages down to 10V.
Some do not work when the supply is 10V or less.

A 9V battery drops to only 6V as it is used.
An MC34071 or TLE2141 opamp works well with a supply down to only 3V and 4V. Both have guaranteed specs with a 5V supply. They have very low distortion and produce full output at 100kHz. Duals and quads are available.

h.z
11-28-2010, 01:59 AM
thanx a lot audioguru and retched. i learn a lot. :)

Georacer
11-28-2010, 12:48 PM
The 741 opamp is 42 years old.

So I guess the reasons they made us use it last year in a project in university where purely historical? :p

bertus
11-28-2010, 12:53 PM
Hello,

Here I have a couple of PDF from Texas Instruments that might interesr you.

Bertus

prateek_ullengal
11-28-2010, 12:53 PM
yes u can operate with 9v as well as 12v....
depends on your application

Audioguru
11-28-2010, 02:11 PM
yes u can operate with 9v as well as 12v....
depends on your application
Many modern opamps work perfectly from a 9V battery that slowly drops to only 6V, but not a 741 opamp.

R!f@@
11-28-2010, 02:32 PM
throw the 741 out of the window.

Get the most reason single ended supply opamp.
Will work with 9V and will last longer in a battery app.

I wonder why Indian uni's still get the students to use those obsolete components.

Oh wait, I forgot.. it's all they have around in thousands.

JoeJester
11-28-2010, 11:37 PM
So I guess the reasons they made us use it last year in a project in university where purely historical? :p

Nope. The reason the universities use the 741 is the same reasons you don't use them. They make great training aids.

beenthere
11-28-2010, 11:55 PM
purely historical?Not at all. Every instructor has a moment of pure pleasure every time another 741 goes in the trash.

Bill_Marsden
11-28-2010, 11:56 PM
Nope. The reason the universities use the 741 is the same reasons you don't use them. They make great training aids.

Agreed. All a standard op amps flaws happen much sooner with a 741.

I mentioned the LM324 as an alternate to the 741. I talked about what a LM324 could do with power supply voltages. It is almost as old as the 741 though, there are much better out there.

For all their flaws, which are legion, they are tough little chips, and a lot of them were made.

Audioguru
11-29-2010, 01:03 AM
I talked about what a LM324 could do with power supply voltages. It is almost as old as the 741 though
The LM324 quad and its sister the LM358 dual are the first "low power" opamps so they have severe crossover distortion that no other opamp has and they have a very low full output bandwidth of only about 2kHz when many other opamps work perfectly up to 100kHz. Their max supply voltage is only 32V when most other opamps have a max supply voltage of 36V and 44V.

MC3317x and MC3407x opamps have many of the features but none of the problems of the old LM324 and LM358 opamps.
But of course these good opamps are not sold in Radio Shack.

Kermit2
11-29-2010, 01:13 AM
Get some 'good' opamps and mark them so to look identical to the 741's your teacher gives you.

The other students will make you rich when they see you have amps that will work in their circuits...

Good for a laugh.

Audioguru
11-29-2010, 01:23 AM
"Any" lousy old opamp will probably work in the teacher's lousy old circuit.

R!f@@
11-29-2010, 01:44 AM
Guys....did it ever occur to you that the "lousy" teacher is here, by any chance.

What if..........?

Audioguru
11-29-2010, 02:15 AM
There actually was a thread on on one of these electronics chat forums where the student was asking for a cheating easy way to make a circuit. Then his teacher replied and flunked the student.

R!f@@
11-29-2010, 04:38 AM
There actually was a thread on on one of these electronics chat forums where the student was asking for a cheating easy way to make a circuit. Then his teacher replied and flunked the student.

Ouch..........!

JoeJester
11-29-2010, 07:29 AM
There actually was a thread on on one of these electronics chat forums where the student was asking for a cheating easy way to make a circuit. Then his teacher replied and flunked the student.

That must have been an interesting confrontation when the student turned in the work.

JoeJester
11-29-2010, 07:30 AM
"Any" lousy old opamp will probably work in the teacher's lousy old circuit.

True. But then the instructor would have to throw away his yellowing notes on the 741 and redo the work on the other "lousy" old opamps.

thatoneguy
11-30-2010, 01:42 AM
I think they are still around simply because there is a demand for them.

There are tens of thousands of schematics of circuits from battery chargers to buffers that have the 741 in the schematic. Until those schematics are updated, or there is a big push for a "Replace the 741 with xxxxxx op amp", there will be questions for it.

Even on the forum, many suggest different (not conflicting, just different) models of op amps as replacements to make the circuit with. This doesn't help somebody just getting started, who has a schematic that has "741" on it, and doesn't know what an op amp is.

Georacer
11-30-2010, 01:11 PM
There actually was a thread on on one of these electronics chat forums where the student was asking for a cheating easy way to make a circuit. Then his teacher replied and flunked the student.

Internet anonymity FTW!
It also helps if you are punctual with your classes... Then you wouldn't need help in homework assignments

...Says the guy who has over 500 posts in helping students have a light time throught their courses...

BillO
12-01-2010, 01:29 AM
Maybe he could use a 709 or 702!

Back in the early 70's the 741s were expensive ($15+! IIRC, that was like day's pay after taxes for me at the time!) and 709s were a bit cheaper for a young nerd like me. They just needed a few extra 'C's and 'R's.

many other opamps work perfectly up to 100kHz.

If I'm not missing something, 'old' chips like the 741 or 709 could run out to 1 MHz effectively.

Audioguru
12-01-2010, 01:39 AM
If I'm not missing something, 'old' chips like the 741 or 709 could run out to 1 MHz effectively.
The 741 drops its full output swing above only 9khz because its slew rate is too low. Its max voltage gain is 1 at about 800kHz, 10 at 80kHz and 100 at only 8kHz.

BillO
12-01-2010, 02:08 AM
Those are for open loop gain.

The GBP for a 741 is 1Mhz which means for unity gain applications you can run it right out to 1Mhz. Depends on the specific application. The GBP was more with a 709 as you could change the frequency compensation.

There is more here on the 741: --> http://www.det.bhtafe.edu.au/amps1/gbp.htm

Audioguru
12-01-2010, 02:24 AM
Guess what? Nobody uses an opamp at its flat-out frequency where its gain is 1 like a piece of wire but its distortion is extremely high. An opamp is normally used at a frequency where its open-loop gain is very high and a lot of negative feedback can be used to reduce the gain to a useable amount, reduce the distortion to be very low and increase the bandwidth.

BillO
12-01-2010, 03:22 AM
Audioguru, I do not want to argue with you. Sure, you personally never use an op-amp at unity gain. Fair enough. You are right, I am wrong. (Edit: BTW, I meant your graphs were for open loop gain. I am talking about a unity gain configuration, DC to 1MHz)

I have, BTW. There are actually many uses in this configuration and for some the resulting bandwidth is handy. Not that I’d use a 741 anymore though.

Okay, hope that point is over. The following is just for discussion purposes as I get unjustly accused of changing the subject a lot, so, just talkin’ here... There are lots of op-amps that can run way beyond 1MHz. While the 741’s ‘possible’ bandwidth is severely limited by the internal ‘Miller effect’ compensation, you could use a 748 (similar vintage and design, uncompensated version of the 741) and configure it with feed-forward compensation, you could get a GBP of 3MHz or more. Today’s run of the mill op-amps can go beyond 100MHz GBP.