Best OpAmp for Rx signal...?

[vistac2000]

Hi to all friends,
I have one question from you...

what is the best opamp to amplification Rx signals ?
we know one of the most important section of a MD is amplify Rx signals to more sensitivity in detection, there are some option that used on MD schematics..., such as NE5532,TL071,TL072,LF356,LF357, or other...

Please help me to choose best opamp to more sensitivity and depth...!!!

thanks...vistac2000

[Geo]

Everything is best for its work. What do you want?? what frequency, what gain, what noise what...what....
In general words look at details for a IC with a big freq bandwidth, high slew rate, small noise figure etc. A good solution is the AD.... IC's

Regards

[vistac2000]

Hi Dear Geo,
Thanks for your answer...

I want to use one opamp for amplification all Rx signals even every weak received signals in one PI metal detector to reach more depth and sensitivity...
we know most PI metal detectors usually work in 100Hz frequency or
under 1kHz ...
What is the best choice for amplification Rx signals in this MD...

what gain is enough for amplification Rx signals in one PI MD?

It is clear that a good opamp must have low noise and high gain...
what is the best solution...?!!!

with best regards... vistac2000

[Geo]

Hi. I dont remember now, but from my experiments, i had the best results with a AD... maybe 877. Maybe later to look at my ATiny4 to see the number.
regards

[Geo]

I remembered....
AD844
Regards

[vistac2000]

Thanks dear Geo,

someone have any other idea ???

with best regards... vistac2000

[porkluvr]

NE5534, NE5534A

If you need the very best, Geo does have a great choice. I think the (8-DIP) NE5534N and AD844N have ALMOST identical pin-out/pin-functions, so with minor changes to offset-null component values you could maybe try either one, even using the same PCB layout. With either device you could strap a compensation capacitor on the bottom of the board if needed. (Or plan for either contingency with appropriate pads.)

NE5534 is not "cutting edge technology" like AD844, but it is probably more readily available, much cheaper, and easier to work with (less prone to instability) by virtue of its (comparatively slow) speed. AD844 needs more careful PCB layout and power supply de-coupling.

Unless you have a very fast PI coil and intend to sample very close to the transmit pulse, you might not see much difference in the two.
For cutting edge performance, try the AD844. For "good" performance, and economy (I need economy)... .

[Geo]

NE5534, NE5534A

If you need the very best, Geo does have a great choice. I think the (8-DIP) NE5534N and AD844N have ALMOST identical pin-out/pin-functions, so with minor changes to offset-null component values you could maybe try either one, even using the same PCB layout. With either device you could strap a compensation capacitor on the bottom of the board if needed. (Or plan for either contingency with appropriate pads.)

NE5534 is not "cutting edge technology" like AD844, but it is probably more readily available, much cheaper, and easier to work with (less prone to instability) by virtue of its (comparatively slow) speed. AD844 needs more careful PCB layout and power supply de-coupling.

Unless you have a very fast PI coil and intend to sample very close to the transmit pulse, you might not see much difference in the two.
For cutting edge performance, try the AD844. For "good" performance, and economy (I need economy)... .

Hi porkluvr.
You have right. I saw difference only at the project of ATiny4, where i gained 1". I Think that LF356, NE5534 and AD844 are pin to pin compatible, because i tried all of them at ATiny

Regards

[Max]

Thanks dear Geo,

someone have any other idea ???

with best regards... vistac2000

Hi,
depends also on which kind of md it is: if PI or VLF etc...

in PIs where you reported 100Hz or under 1KHz you can use often ne5534 or 5534a like porkluvr stated: old choice but valid.

Or AD pieces... I have to say they are obviously really nice there. I would also consider the LF356/357 (very nice also and widely used in depth PIs of past years) and the OP27/OP37 things also (lower noise).

Now... the problem is also what's after the preamp... I mean if you have double sampling (or more samples) you can take advantages of also not state of the art parts cause you have averaged noise there....

In simple one sample things (old stuff.... educational only like e.g. sandbanks PI) you'll get more juice from better , lower noise parts... but that's obvious: more noise there at start of amplifiers chain and you'll be lost in space with erratic behaviour cause noise is not averaged in single sample PIs.

Also... if you have an ADC right after the preamp you'll take much advantage of less noised signal... visible I mean, that's why often an AD is required in such designs... well things are quite advanced if you have the adc right there...

Anyway, you must also find these parts... sometimes it's not so easy in some places, are you aware of that !?

Hope you'll find a good one... like an AD, really nice parts.

Kind regards,
Max

[detectoman]

hello all
for my in my poor understands, i put preference to, op amp, lm 358, or major, ic 4558

[vistac2000]

Hi to all friends,

what about LM series opamp such as LM386,LM358,...etc
are these opamps good for one PI MD???

with best regards... vistac2000

[porkluvr]

Hi to all friends,

what about LM series opamp such as LM386,LM358,...etc
are these opamps good for one PI MD???

Sometimes you will get bad advice on parts substitutions so you should know that you can go to all of the manufacturers' website and download datasheets for any of their products for free! If you don't know the manufacturer, or if the part is obsolete, you can still usually get a datasheet from one of these links:
http://www.datasheetcatalog.com/
http://www.datasheet.in/
There are more.

Look for key specifications like gain-bandwidth product, slew rate, noise, power supply current, IC package and pinout, number of amplifiers per package, DC offset voltage, power supply current, and etc.

You probably should do some Google searching for "opamp cookbook" or something like that to get some quick-and-dirty book-learning. I'm kind of busy right now but I'll try to find and post some good knowledge links here in a day or so.

Some of the amplifier specifications are easier to understand than others, and sometimes different manufacturers use different methods of expressing the same information, so it takes a little bit of thought when making comparisons under those conditions.

You need acrobat reader for most of the datasheets.
Here's a hint: If you want to be able to compare two products side-by-side you can save one datasheet to your hard drive then open it, and then go to the first link I gave you and get the other datasheet which will open in a seperate window. Of course, it's easier if you have a dual monitor video card and two monitors, but it can still speed things up even if you don't.

Now about the LM358 and LM386. LM358 is too slow and noisy to be of much use for a front-end amplifier, but it is inexpensive and consumes little power. It is adequate for a lot of mid-level amplification and integration chores so you should probably have a few around. LM386 is usually used as an audio output amplifier to drive a speaker. ("Look at the data sheets, don't take mine or anyone else's word for it".)

One other thing... for some applications you should place more importance on certain specs than in other appps. For instance, if you are mainly interested in a high power PI where you will probably be powering it with a fairly large battery, you don't really need to be extremely worried about "power supply current" in your opamps. But if you're doing an IB that you'll power with a little dinky battery then you would definately want to pay attention to that spec. Just my opinion.

[Max]

Hi to all friends,

what about LM series opamp such as LM386,LM358,...etc
are these opamps good for one PI MD???

with best regards... vistac2000

Hi,
no.

lm386 is an audio amplifier so forget about. The lm358 is too noisy for a serious role like a preamp has...so forget both.

Kind regards,
Max

[porkluvr]

I once read that the LM358 is the most widely used (dual?) opamp in the world. But that still does not make it the BEST opamp in the world, it's only because it's so darn cheap (and won't drain your batteries so fast as some of the others).

http://www.analog.com/library/analog..._handbook.html
http://focus.ti.com/lit/an/sboa092a/sboa092a.pdf
http://en.wikipedia.org/wiki/Operational_amplifier
http://www.williamson-labs.com/480_opam.htm
http://www.ee.nmt.edu/~thomas/data_s...p-slod006a.pdf

[Max]

I once read that the LM358 is the most widely used (dual?) opamp in the world. But that still does not make it the BEST opamp in the world, it's only because it's so darn cheap (and won't drain your batteries so fast as some of the others).

http://www.analog.com/library/analog..._handbook.html
http://focus.ti.com/lit/an/sboa092a/sboa092a.pdf
http://en.wikipedia.org/wiki/Operational_amplifier
http://www.williamson-labs.com/480_opam.htm
http://www.ee.nmt.edu/~thomas/data_sheets/op-amp-slod006a.pdf

Hi,
yes, I read something , somewhere... who care.... it's like getting a meal at MacDonald's once a year (maybe) could be safe...enough

But people that go there everyday....cause it's dang cheap (or cause have some food related compulsive disorder....) will end soon... with a big blast of their liver!

LM358 is to me...like junk food... one can also live with that (for a while) but will pay everything sooner or later.

In a PI MD using that stuff is good just for some later blocks.... where noise is secondary issue.... but not in critical parts.

It's like, coming back to MacDonald's example, trying to lose excess weight eating just proteins and fat (a big series of luxury burgers ) and ending soon with some gout!

We wanna less noise... less troubles... and lm358 is a bad guy!

Kind regards,
Max