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.

 

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.

 

"Any" lousy old opamp will probably work in the teacher's lousy old circuit.

 

Guys....did it ever occur to you that the "lousy" teacher is here, by any chance.

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

 

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.

 

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..........!

 

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.

 

"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.

 

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.

 

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...

 

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.

 

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.

 

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

 

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.

 

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.