Getting En from NV

[[email protected]]

Hi,

I'm looking at a supposedly low noise N-JFET (NTE458), which only
supplies the Noise Voltage data, as 15mV (Id=0.5mA, Rg=1K, f= 10Hz to
1KHz, Vg=-3db). Taking that down to 1Hz gets 15mV / sqrt(1000-10) ~=
477 uV/rtHz. That's a lot of noise so I presume it's due to 1/f noise.
Is there a way of getting En at say 1KHz?

http://www.nteinc.com/specs/400to499/pdf/nte458.pdf

Thanks,
Paul

 

[John Larkin]

Hi,

I'm looking at a supposedly low noise N-JFET (NTE458), which only
supplies the Noise Voltage data, as 15mV (Id=0.5mA, Rg=1K, f= 10Hz to
1KHz, Vg=-3db). Taking that down to 1Hz gets 15mV / sqrt(1000-10) ~=
477 uV/rtHz. That's a lot of noise so I presume it's due to 1/f noise.
Is there a way of getting En at say 1KHz?

http://www.nteinc.com/specs/400to499/pdf/nte458.pdf

Thanks,
Paul

That datasheet is total nonsense. How does one measure "Noise
Frequency" in dB? And I have no idea what the 15 mV "noise voltage"
might mean, and I suspect they don't, either.

Doesn't NTE sell floor sweepings into the repair market?

John

 

[Pooh Bear]

That datasheet is total nonsense. How does one measure "Noise
Frequency" in dB? And I have no idea what the 15 mV "noise voltage"
might mean, and I suspect they don't, either.

15 uV ought to be more like it !

Doesn't NTE sell floor sweepings into the repair market?

Who *are* NTE anyway and why do their products get mentioned in ngs so often ?

Graham

 

[Chris]

Pooh Bear wrote:

Who *are* NTE anyway and why do their products get mentioned in ngs so often ?

Graham

Hi, Graham. NTE is the largest seller of general repair parts for
radio, television and consumer electronics.

They don't manufacture much of anything -- they get representative
parts and have their house (NTE) number printed on them.

Several advantages to NTE parts here. First, if you live close to any
metropolitan area, you can get it *today* -- that can be important if
tomorrow's too late. They have many local distributors through the
TV/Radio/consumer electronics repair network. If you live, say, in
Chicago, you can just drive to one of many different sources, and get
these parts until at least 7:00pm on weekdays. This has saved me many
times on ultra-urgent prototypes, when tomorrow's too late.

Second, in order to minimize the number of discrete semis they carry,
they purchase standard parts and have them tested to a sometimes more
rigorous spec, so that the one part can be a substitute for many
different discrete transistors or diodes. You just look up the
standard part number in their cross-reference to get the NTE number.
The cross-reference is available in their catalog, or on their website.

Third, they're good at getting in end-of-life buys, so if you need a
small quantity of something that's been obsoleted, you can look there
before going to a broker. They generally charge about what a broker
will, and their parts are top quality. Brokers, sometimes not so much.

They also carry resistors, caps, and a line of techie stuff, and are
good guys -- except that they charge premium prices, of course.

But if you need it NOW, that's no problem. I find it to be a good last
chance source for engineering prototype parts, especially transistors
and standard ICs. For a hobbyist, getting these parts can be as simple
as driving down to the local TV repair shop.

Their data sheets do occasionally have errors in them, as this one
apparently does.

Cheers
Chris

 

[Phil Allison]

http://www.nteinc.com/specs/400to499/pdf/nte458.pdf

** That last line with Noise Voltage data is plain wrong.

Based on the noise figure data, the correct noise voltage numbers are 0.15
and 0.2 uV.

This is consistent with a low noise J-fet like the 2N5459.




........ Phil

 

[[email protected]]

Pooh Bear wrote:


Hi, Graham. NTE is the largest seller of general repair parts for
radio, television and consumer electronics.

They don't manufacture much of anything -- they get representative
parts and have their house (NTE) number printed on them.

Several advantages to NTE parts here. First, if you live close to any
metropolitan area, you can get it *today* -- that can be important if
tomorrow's too late. They have many local distributors through the
TV/Radio/consumer electronics repair network. If you live, say, in
Chicago, you can just drive to one of many different sources, and get
these parts until at least 7:00pm on weekdays. This has saved me many
times on ultra-urgent prototypes, when tomorrow's too late.

Second, in order to minimize the number of discrete semis they carry,
they purchase standard parts and have them tested to a sometimes more
rigorous spec, so that the one part can be a substitute for many
different discrete transistors or diodes. You just look up the
standard part number in their cross-reference to get the NTE number.
The cross-reference is available in their catalog, or on their website.

Third, they're good at getting in end-of-life buys, so if you need a
small quantity of something that's been obsoleted, you can look there
before going to a broker. They generally charge about what a broker
will, and their parts are top quality. Brokers, sometimes not so much.

They also carry resistors, caps, and a line of techie stuff, and are
good guys -- except that they charge premium prices, of course.

But if you need it NOW, that's no problem. I find it to be a good last
chance source for engineering prototype parts, especially transistors
and standard ICs. For a hobbyist, getting these parts can be as simple
as driving down to the local TV repair shop.

Their data sheets do occasionally have errors in them, as this one
apparently does.

Cheers
Chris

Often I use a reverse NTE cross reference ->

http://www.kenselectronics.com/brands/nte.htm

, but sometimes that website doesn't know the reverse part; e.g., for
NTE458 they merely show "N-chan JFET"

You're right Chris about NTE being quick and convenient. I just wish
they would easily supply the reverse part #. Personally I usually find
NTE's datasheets lacking a great deal. So it's not like I want to find
the reverse part # and buy from another manufacturer, but that might be
nice. ;-) Usually I need to see a detailed datasheet. Is there a way of
finding all the NTE reverse cross reference part #'s?

Paul

 

[Chris]

Often I use a reverse NTE cross reference ->

http://www.kenselectronics.com/brands/nte.htm

, but sometimes that website doesn't know the reverse part; e.g., for
NTE458 they merely show "N-chan JFET"

You're right Chris about NTE being quick and convenient. I just wish
they would easily supply the reverse part #. Personally I usually find
NTE's datasheets lacking a great deal. So it's not like I want to find
the reverse part # and buy from another manufacturer, but that might be
nice. ;-) Usually I need to see a detailed datasheet. Is there a way of
finding all the NTE reverse cross reference part #'s?

Paul

Hi, Paul. Reverse cross-referencing would probably be about the worst
thing for their business model. Once or twice over the years, I'll
admit to flipping through the 2N and 3N pages of the cross-reference
catalog, looking for the NTE or ECG number so I could substitute
something I had on hand. (O shame! O indignity!)

If you take the time to figure out what's going on in the circuit, you
can pretty well figure out what part you need. And that should take
less time than flipping through the pages. But on the other hand, if
you're repairing an old engineering prototype without docs that has an
ECG or NTE part, that may be a valid choice if you're in a big hurry.

On the downside, the NTE cross isn't always perfect. It usually works
-- not always.

If you buy the concept that you're replacing a part with a guaranteed
"as-good-as" or superior part with NTE, you're accepting that going the
other way may very well result in your replacing with an inferior part.

And even if either of two parts can be replaced by one NTE part, that
doesn't necessarily make them equivalents to each other. (Try using
translation websites to go, say, from English to German, and then back
again. Note the potentially hilarious results. Not so hilarious if
your fix doesn't work.)

But the concept of a reverse cross-reference is a pretty good one, I'd
guess. You might have to scan in all the pages of the cross-reference,
then plug the data into a ginormous spreadsheet. And of course, if you
ever tried to sell it, NTE would come down on you like a ton of bricks.

Cheers
Chris

 

[John Larkin]

You're right Chris about NTE being quick and convenient. I just wish
they would easily supply the reverse part #. Personally I usually find
NTE's datasheets lacking a great deal.

The datasheets are vague so that they can buy whatever's cheapest this
week, stick their number on it, and sell you that.

You can buy real parts, with real datasheets, from Mouser or Digikey,
only cheaper.

John

 

[Michael A. Terrell]

Hi, Paul. Reverse cross-referencing would probably be about the worst
thing for their business model. Once or twice over the years, I'll
admit to flipping through the 2N and 3N pages of the cross-reference
catalog, looking for the NTE or ECG number so I could substitute
something I had on hand. (O shame! O indignity!)

If you take the time to figure out what's going on in the circuit, you
can pretty well figure out what part you need. And that should take
less time than flipping through the pages. But on the other hand, if
you're repairing an old engineering prototype without docs that has an
ECG or NTE part, that may be a valid choice if you're in a big hurry.

On the downside, the NTE cross isn't always perfect. It usually works
-- not always.

If you buy the concept that you're replacing a part with a guaranteed
"as-good-as" or superior part with NTE, you're accepting that going the
other way may very well result in your replacing with an inferior part.

And even if either of two parts can be replaced by one NTE part, that
doesn't necessarily make them equivalents to each other. (Try using
translation websites to go, say, from English to German, and then back
again. Note the potentially hilarious results. Not so hilarious if
your fix doesn't work.)

But the concept of a reverse cross-reference is a pretty good one, I'd
guess. You might have to scan in all the pages of the cross-reference,
then plug the data into a ginormous spreadsheet. And of course, if you
ever tried to sell it, NTE would come down on you like a ton of bricks.

Cheers
Chris

I just sort a lot of leftover semiconductors by the ECG/NTE cross
reference and see what I have on hand when I need a part. If a drawer
fills up, I sort it out by part number of anything I find more than a
dozen or so, and put them into their own drawers. Of course, I have
over 20, 50 drawer parts cabinets full of sorted parts.

The bad thing is that they delete a cross reference when they
obsolete a part number, so you may have the part in stock, but its no
longer in the book or software.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida