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2N7000's Vgs

B

Boki

Jan 1, 1970
0
Hi All,

The FET ( ex: 2N7000 )'s Vgs is about 3V .... ( this is very different
to VLSI )


My power supply is only 2.4V, I have to do a level shit and then turn
on this mos.


How about the 0.7V ( around ) MOS, is that expesive?

Thanks.

( of course, I will check the great information/website/all that you
have provided, thanks a lot )

Best regards,
Boki.
 
J

Joerg

Jan 1, 1970
0
Hello Boki,
The FET ( ex: 2N7000 )'s Vgs is about 3V .... ( this is very different
to VLSI )

My power supply is only 2.4V, I have to do a level shit and then turn
on this mos.
Click to expand...

Level shit? That was a good one :)
How about the 0.7V ( around ) MOS, is that expesive?
Click to expand...

You can't buy that in a discrete FET. There are some that are called
"logic-level FET" but look at the fine print. Often they are just
scraping by at 5V, some at 3.3V. But 2.4V is too low for my taste, I'd
certainly go with bipolar transistors there or with level shift.

Also, don't rely solely on the Vgs/Rds graphs in the data sheet for a
design. Those represent "typical" values. There needs to be hard data,
like maximum Rdson at your desired gate voltage.

Regards, Joerg
 
L

linnix

Jan 1, 1970
0
Boki said:
Hi All,

The FET ( ex: 2N7000 )'s Vgs is about 3V .... ( this is very different
to VLSI )
Click to expand...

I read 2.1V typical and 3V max.
My power supply is only 2.4V, I have to do a level shit and then turn
on this mos.


How about the 0.7V ( around ) MOS, is that expesive?
Click to expand...

What part number?
 
B

Boki

Jan 1, 1970
0
Joerg 寫�：
Hello Boki,


Level shit? That was a good one :)
Click to expand...

sorry, typo ; )
You can't buy that in a discrete FET. There are some that are called
"logic-level FET" but look at the fine print. Often they are just
scraping by at 5V, some at 3.3V. But 2.4V is too low for my taste, I'd
certainly go with bipolar transistors there or with level shift.

Also, don't rely solely on the Vgs/Rds graphs in the data sheet for a
design. Those represent "typical" values. There needs to be hard data,
like maximum Rdson at your desired gate voltage.

Regards, Joerg
Click to expand...

I got it, thank you very much.

Best regards,
Boki.
 
M

Mac

Jan 1, 1970
0
Hi All,

The FET ( ex: 2N7000 )'s Vgs is about 3V .... ( this is very different
to VLSI )


My power supply is only 2.4V, I have to do a level shit and then turn
on this mos.


How about the 0.7V ( around ) MOS, is that expesive?
Click to expand...

??
I don't think you will find discrete MOS with 0.7V Vgs(th).

I think there is discreet CMOS logic which will work OK down at that
level.

And there are discrete FET's out there which will reliably (guaranteed by
datasheet) turn on at 2.4V. You can sniff around at zetex, for example.

These parts are much more expensive than a 2n7002.
Thanks.

( of course, I will check the great information/website/all that you
have provided, thanks a lot )

Best regards,
Boki.
Click to expand...

Good luck, Boki. I have a feeling you will need it. ;-)

--Mac
 
M

Mac

Jan 1, 1970
0
Hi All,

The FET ( ex: 2N7000 )'s Vgs is about 3V .... ( this is very different
to VLSI )


My power supply is only 2.4V, I have to do a level shit and then turn
on this mos.


How about the 0.7V ( around ) MOS, is that expesive?

Thanks.

( of course, I will check the great information/website/all that you
have provided, thanks a lot )

Best regards,
Boki.
Click to expand...

The BSS138 has a max Vgs(th) of 1.5 V at Ids=1mA, which is a higher
current than many other threshold voltages are specified at.

With low-threshold discretes, you may find that the gate capacitance will
be problematic, depending on what you are trying to do.

--Mac
 
L

linnix

Jan 1, 1970
0
Boki said:
linnix 寫�：


2N7000
Click to expand...

2N7000 has typical 2.1V Vgs. So if you buy a batch of them, most will
turn on at 2.1V. However, even if you can turn it on with 2.4V, you
can hardly drive anything. Unless you have another power source
(step-up from 2.4V) for the drain, there won't be enough power for the
load. Can you tell us more about what you are trying to do?
 
D

[email protected]

Jan 1, 1970
0
Mac said:
The BSS138 has a max Vgs(th) of 1.5 V at Ids=1mA, which is a higher
current than many other threshold voltages are specified at.
Click to expand...

The BSS138 is about the nicest low Vgs(th) jelly-bean MOSFET I've
seen. SOT-23, 3.5ohms Rds(on), and only $.07 from OnSemi & Siemens--or
only $.05 from Fairchild--for a reel from DigiKey. And I've got a few
hundred in my possession. Kewl.
With low-threshold discretes, you may find that the gate capacitance will
be problematic, depending on what you are trying to do.

--Mac
Click to expand...

Ciss(max) = 50pF (Zetex), 27pF (Fairchild) -- not terrible. By
comparison, Fairchild's 2n7000/2n7002 Ciss(max) = 50pF, Vgs(th) (max) =
3v @ 1mA.

Cheers,
James Arthur
 
U

Uwe Bonnes

Jan 1, 1970
0
Boki said:
Hi All,
Click to expand...
The FET ( ex: 2N7000 )'s Vgs is about 3V .... ( this is very different
to VLSI )

My power supply is only 2.4V, I have to do a level shit and then turn
on this mos.

How about the 0.7V ( around ) MOS, is that expesive?

( of course, I will check the great information/website/all that you
have provided, thanks a lot )
Click to expand...

Look at Philips ...UN series. They are spezified at 1.8 V VGS
 
R

Richard H.

Jan 1, 1970
0
The BSS138 is about the nicest low Vgs(th) jelly-bean MOSFET I've
seen. SOT-23, 3.5ohms Rds(on), and only $.07 from OnSemi & Siemens--or
only $.05 from Fairchild--for a reel from DigiKey. And I've got a few
hundred in my possession. Kewl.




Ciss(max) = 50pF (Zetex), 27pF (Fairchild) -- not terrible. By
comparison, Fairchild's 2n7000/2n7002 Ciss(max) = 50pF, Vgs(th) (max) =
3v @ 1mA.
Click to expand...

ON Semi's NTA7002N seems attractive on the surface - Vgs(th)=1.0v
(100uA); Ciss 11.5pF. It looks like ~25mA @ 1.5v and 154mA @ Vgs=2.0v.
$.04 in reel; tiny SC-75 package.
http://www.onsemi.com/pub/Collateral/NTA7002N-D.PDF

Is there a "gotcha" with this one that I'm not seeing?

I'm not deperate enough to pay ON $11 to ship a "free" sample yet :),
and I'm not quite ready to buy a whole reel.


Curiously, the SOT-23 version from ON has very different specs. I'd
have thought they used the same die for both, but the package alone
can't account for these differences, can it?

The SOT-23 version Vgs(th)=1.0 to 2.5 (@ 250uA); Ciss is 50pF; it'll do
115mA, but at Vgs=8v. http://www.onsemi.com/pub/Collateral/2N7002L-D.PDF
 
K

Ken Smith

Jan 1, 1970
0
linnix said:
2N7000 has typical 2.1V Vgs. So if you buy a batch of them, most will
turn on at 2.1V.
Click to expand...

This is not true. If you buy 1000 transistors from 1000 different batches
they will average somewhere near 2.1V. The ones they make on Tuesday
morning will be more tightly clustered around some other number.
 
B

Boki

Jan 1, 1970
0
Uwe Bonnes 寫�：
Look at Philips ...UN series. They are spezified at 1.8 V VGS

--
Uwe Bonnes [email protected]-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
Click to expand...


Hi

Could you please help to provide the link? Thank you very much.

because I can't find it...

here is the link I found:
http://www.semiconductors.philips.com/products/discretes/index.html

I can see rf / power mos only ....


Best regards,
Boki.
 
B

Boki

Jan 1, 1970
0
linnix 寫�：
2N7000 has typical 2.1V Vgs. So if you buy a batch of them, most will
turn on at 2.1V. However, even if you can turn it on with 2.4V, you
can hardly drive anything. Unless you have another power source
(step-up from 2.4V) for the drain, there won't be enough power for the
load. Can you tell us more about what you are trying to do?
Click to expand...

Hi,

Here is the circuit I am going to do: ( I want to replace transistors )
http://photos1.blogger.com/blogger/1641/2018/1600/led.png

Here is the model
http://www.fairchildsemi.com/models/email_model_file.jsp?file=2N7000.mod

Simulation result:
http://photos1.blogger.com/blogger/1641/2018/1600/2n7000_test.png
http://photos1.blogger.com/blogger/1641/2018/1600/2N7000.png

It seems that the Vgs is about 3V, I don't know why it is about
2.4V..., could you please advice?

Thank you very much.

Best regards,
Boki.
 
R

Richard H.

Jan 1, 1970
0
Richard said:
ON Semi's NTA7002N seems attractive on the surface - Vgs(th)=1.0v
(100uA); Ciss 11.5pF. It looks like ~25mA @ 1.5v and 154mA @ Vgs=2.0v.
$.04 in reel; tiny SC-75 package.
http://www.onsemi.com/pub/Collateral/NTA7002N-D.PDF

Is there a "gotcha" with this one that I'm not seeing?
Click to expand...

Ah... maybe the fact that everyone's got it on 25 week leadtimes...

However, these also look interesting and are in-stock in cut tape from
Digi-key, though at 2-4x the cost:

Vgs(th)=1.0; 11.5pF; 238mA:
http://www.onsemi.com/pub/Collateral/NTA4001N-D.PDF

Vgs(th)=0.76v; 110pF; 915mA:
http://www.onsemi.com/pub/Collateral/NTA4153N-D.PDF
 
D

[email protected]

Jan 1, 1970
0
Richard said:
ON Semi's NTA7002N seems attractive on the surface - Vgs(th)=1.0v
(100uA); Ciss 11.5pF. It looks like ~25mA @ 1.5v and 154mA @ Vgs=2.0v.
$.04 in reel; tiny SC-75 package.
http://www.onsemi.com/pub/Collateral/NTA7002N-D.PDF

Is there a "gotcha" with this one that I'm not seeing?
Click to expand...

I like the small package (SOT-23 is awfully gigantic these days,
isn't it?), and the reasonable price. That part's typical Vgs(th) is
spec'd at 1.0v @ 100uA, but it's 1.5v worst-case, versus Fairchild's
BSS138's Vgs(th) of 1.5v @ 1mA, worst-case, so the BSS138 comes on
harder, earlier (i.e. at lower voltages).

Ciss is only 12pF (typ) @ 5V Vds, beating the BSS138's 27pF (max)
handily.

Nice part.

James Arthur
 
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