replacement for 741

Oh I think the old lm741 will be around for a LONG time.

I would use the plastic DIP version as the cerdip and metal cans are rapidly dissappearing. Nation even recommends an improved version on their website but does not have the telltale "Not for NEW DESIGN" monicer.

Interesting project. If you want a good difference amplifier check the Texas Instruments website at

and go to the IA section, lots of outstanding performers there, both TI and Burr-Brown. These parts are available from both Mouser and Digikey.

I don't think that was his point. The 741 is pretty old, and likely is the oldest IC op-amp still in common use. They were a decade or so old when the TL081 came along, and those were pretty hot stuff almost thirty years ago compared to the 741.

Yes, the 741 does not seem to be about to disappear, and it says quite a bit about it that it is getting close to forty years old and it can still be useful.

But the fact that it is old means that other things have come along, and the 741 was never so great in a lot of areas, and the more recent devices (even those from 25 to 30 years ago, like the TL081) are of course better devices if you need the better specs.

Michael

That 741 design has been updated for modern processes and to correct other problems. The part number may be "old" but the actual part in hand is quite "new." The OP may believe he is using an actual chip manufactured way back before he was even born.

In message , dated Sun, 27 Aug 2006, snipped-for-privacy@triton.net writes

Single op-amps of the 'cooking' variety are not much used now. To get a single, you are likely to pay for a device much superior to the 741, which you don't need.

There are LOTS of duals, widely available at very low prices: TL072, MC4558....

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

I just replaced a few 741 type op amps in some old equipment with some op97. The nulling is slightly different.

You need to determine what specifications you realy need.

Colin =^.^=

schreef in bericht news: snipped-for-privacy@i42g2000cwa.googlegroups.com...

Joe,

Last time I needed a 741 (for a very old design) and my supplier had none directly available I used a CA3041 without any problem.

petrus bitbyter

Thanks to everyone who responded. As to the specifications required for the op-amp, unfortunately I don't know what is important in my application. The 741 seemed to work adequately in the first circuit I made. I thought if there were any newer pin-for-pin replacements for the 741, maybe I could just pop one in the socket, and see if there was any difference. I don't know enough about electronics to do much analysis, I just wanted to use the "try it and see" approach. It seems the TL081 has gone out of production. National Semiconductor says that LMC6081 is a replacement, so I may try that one.

The price isn't much of a factor, I'm just looking for an op-amp with good all-round properties (yes, I know that's vague, but I don't have enough knowledge to phrase it any other way). Or it may be better to use a ready-made difference amplifier chip (which is the kind of circuit I actually need) using one of those made by Texas Instruments, as was suggested. After all is said and done, I may not get any better performance compared to the 741, but I didn't want to have a problem because I didn't spend a few extra bucks for a more up-to-date op-amp.

Thanks again, Joe

The 741 is very outdated. The LF156 is the military version of National Semiconductor integrated circuit FET-input op amp from the early 1970's

- if you don't want a -55C to 125C temperature range, go for the industrial LF256 ( -25C to 85C) or the much cheaper and easily available commercial LF356 (0C to 70C).

The FET input stage offers a low leakage current, very low current noise, relatively low voltage noise - 12nVper root Hz with a noise corner around 100Hz and it doesn't go non-linear until the voltage excursions across the input get up to close to a volt.

The output stage is much better behaved than that of the 741, with

12V/usec of slew rate and the capacity to drive up to about 1000pF of capacitative load without oscillating.

The TL081 was a Texas Instruments me-too part, closer to National Semiconductor's cheaper (and later) LF351 single, LF353 dual and LF347 quad FET-input parts.

There are lots of similar parts avaialble - cheaper, faster, more compact, lower-powered etc and we'd need to know more about your application to recommend anything specific.

The AD8131 isn't something you'd want to hook up directly to photodiode, unless you had a very large number of photons to play with.

The Burr-Brown - now Texas Instruments - OPA-656 could be a useful part

It is useful where you need more bandwidth (230MHz) and lower noise (7nV per root Hz) than you can get from the LF356 and similar moderately up-nmarket parts. It tends to show up in photo-diode current-to-voltage converter stages, as discussed in the data sheet, where you can need a lot of bandwidth in the op-amp to get 741 type bandwidths out of the photodiode.

--
Bill Sloman, Nijmegen

In message , dated Sun, 27 Aug 2006, snipped-for-privacy@triton.net writes

Yes, there are plenty, but you may not get them from broad-line distributors.

Difference amplifiers will require circuit changes. Don't go there.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

In message , dated Sun, 27 Aug 2006, snipped-for-privacy@ieee.org writes

The OP has now told us his knowledge of electronics is limited. So a 230 MHz part is definitely contra-indicated!

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

LF351 is suposedly pin for pin replacement, and is available from hobby stores.

Colin =^.^=

In message , dated Sun, 27 Aug

2006, colin writes

Indeed; it is very similar.

-- OOO - Own Opinions Only. Try

and

2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Some factors that might be important are (and typical value for 741):

Speed (gain bandwidth product) 1 MHz Input offset voltage error 1 mV Input bias current 10 nA Voltage noise 23 n/sqrt(Hz) Current noise ? Offset nulling connections and method (more important for plug in compatibility than for new design) Pins 1 and 5 to ends of pot, with wiper to V- Supply voltage range ~7 to 44 V Input common mode voltage range V+ -3 V to V- +3V

To upgrade a 741, you might look for an amp that has a bit higher gain bandwidth product, lower offset voltage and current, lower current and voltage noise, adequate supply range and similar offset nulling method.

That last one severely limits the choices, since the 741's nulling connections and method is not very ordinary.

If your circuit does not include offset nulling, you still have to confirm that that there is nothing incompatible with the substitute amp, connected to pins 1 or 5.

The LF351 is a 4 MHz amp with somewhat compatible offset nulling, rated for up to 36 volt total supply.

Its offset voltage is 5 mV (worse than the 741) Its bias current is lower, because it is a jfet input type, instead of a junction transistor type. So I would expect it to be an improvement only if speed or low bias current (high source impedance) were important.

Anybody who is fooling around with photodiodes and lasers to make a holographic fringe locker is either going to learn quite a lot of electronics quite rapidly, or or is going to move into a less demanding line of business. The OPA-656 is a good choice of amplifier for quite a few applications in that area, even if it is fast enough to frighten people can still find places where they can use a 741.

--
Bill Sloman, Nijmegen

Unless you specifically *need* a high noise level (the 741 makes noise!), almost any modern op-amp will be a significant improvement. TL081 and TL071 both come to mind. Allied, Newark, Digi-Key, etc., should definitely have both of these. The part number has a suffix to indicate the package and temperature range (you want 8-pin DIP, industrial temperature range).

First off, sorry for google grouping but my ISP's news server updates once a week, ie it's useless.

I'm currently designing an anlog control system for a cooler I'm making. Lots of anolog maths (mainly subtraction with some PID and multiplication) handled by op-amps. Looking for a quad op-amp package with low power and low offset (or easy offset nulling) as my main requirements, highest frequency will be around 0.25 Hz (and that's only if everything else goes very pear-shaped). Low noise would be useful but looking at the units they are in it doesn't seem a problem at low frequencies (correct?). Need to be able to accept and output signals from 0 to 12V inclusive. Was planning to run them from +-15V rails but I can easily change that. Price is also a deffinate consideration. Any recommendations would be greatly apreciated.

Edward

Have a look at the LT1014 quad - it is Linear Technology's version of what the LM324 ought to have been, with worst case offest voltages of about 1mV and around 22nV per root Hz voltage noise down to 10Hz. It is ex-stock from Farnell, but does cost about $10 in small quantities.

If you want really low off-set voltages, you could look at their chopper stabilised parts - LTC1053 - also available from Farnell, but even more expensive and can't take more than 16.5V between V+ adn V-.

Tha Analog Devices AD8630

is cheaper, but can't take more than 6V.

National Semiconductor has similar devices.

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Bill Sloman, Nijmegen

Sorry about roducing two responses to the same post, but this post is pretty much orthogonal to the last one.

Why on earth are you designing a analog control system for a cooler? If your fastest response is at around 0.25Hz and you need mutiplication, a decent A/D converter (20-bit sigma-delta) and a microprocessor are the way to go.

Check out

Sloman A.W., Buggs P., Molloy J., and Stewart D. "A microcontroller-based driver to stabilise the temperature of an optical stage to 1mK in the range 4C to 38C, using a Peltier heat pump and a thermistor sensor" Measurement Science and Technology, 7 1653-64 (1996)

and

Sloman A.W. "Comment on 'Implementing of a precision fast thermoelectric cooler controller using a personal computer parallel port connection and ADV8830 controller'[Rev.Sci. Instrum. 74, 3862 (2003)]" Review of Scientific Instruments, 75 788-9 (2004).

which includes some discussion of why digital is the way to go. I've got .pdf pre-prints of both papers - e-mail me if you want copies.

--
Bill Sloman, Nijmegen