Several questions about 2N7000 transistors

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Wendy

Joined Mar 24, 2008
22,990
What is the gate voltage required to turn this transistor on? I do not believe this is a logic level mosfet device.

What if any is the complementary transistor for this device
 

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SamR

Joined Mar 19, 2019
4,345
Well, if you use it as a switch for 5V logic... According to Google, the P-channel equivalent is the BS250P.
 
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crutschow

Joined Mar 14, 2008
30,463
I do not believe this is a logic level mosfet device.
It's not quite a true logic-level device as it has a maximum Vgs(th) of 3V and requires Vgs=10V to get the minimum on-resistance value, but it will conduct 75mA with a low drop at a Vgs of 4.5V.
So with a 5V Vgs you should be able to use it as a switch up to about 100mA Ids or so

Obviously won't work worst-case for a 3.3V logic-level.

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Papabravo

Joined Feb 24, 2006
19,023
Logic-level is no longer an unambiguous or precise concept in the era of low voltage CMOS parts that operate with a Vcc of 1.65 volts. For example, the 74LVC1G family of parts.
 

Papabravo

Joined Feb 24, 2006
19,023
So is there a complementary device?
If there is I haven't heard of it or had occasion to use one. When it comes to MOS structures, the notion of complementary is not equivalent to the same concept for Bipolar Junction Transistors. Feature size and die area would be different for a truly complementary device. P-channel devices are less numerous and less diverse than their N-channel cousins. On integrated circuits P-channel devices show up rarely. Why do you ask?
 

Papabravo

Joined Feb 24, 2006
19,023
That's also true for bipolar devices.
There were discrete BJT's before there were integrated circuits. With enhancement mode MOS devices, the discrete parts and the ICs were developed at roughly the same time. Discrete PMOS transistors failed to find a niche in that environment. That's my recollection and my hypothesis. As always, I could be wrong.
 

Papabravo

Joined Feb 24, 2006
19,023
It might be useful to make the occasional CMOS style push pull configuration now and again.
That is often done with a pair of NMOS devices and a bootstrap Gate voltage supply, or an integrated gate driver, which may or may not have an internal PMOS device.
 
2N7000 is a very old DMOS mosfet, among the first in a TO-92 package. Came out around 1982 same as Siliconix VN10K. I use the 2N7000K which has the essential gate protection zener, because these parts are super susceptable to ESD.
I dislike the name "Fetlington" one guy used for it, that's something totally different - a compound Darlington using a JFET. There's no "ling" in a mosfet lol.

Look at BSS138 and BSS84 (P-ch) I think they are better in the world of 3-5V gate drive and SOT-23.
For 3.3V drive small power mosfets there's not many out there.
 

Papabravo

Joined Feb 24, 2006
19,023
2N7000 is a very old DMOS mosfet, among the first in a TO-92 package. Came out around 1982 same as Siliconix VN10K. I use the 2N7000K which has the essential gate protection zener, because these parts are super susceptable to ESD.
I dislike the name "Fetlington" one guy used for it, that's something totally different - a compound Darlington using a JFET. There's no "ling" in a mosfet lol.

Look at BSS138 and BSS84 (P-ch) I think they are better in the world of 3-5V gate drive and SOT-23.
For 3.3V drive small power mosfets there's not many out there.
There are so many good options for properly driving a MOSFET that it seems sub-optimal to go looking for specialty parts that may be in short supply.
 
The 2N7000 is older (30 years) through-hole TO-92 and people have moved on to SOT-23. MOSFET technology did greatly improve since then - lower VGS (on) and RDS (on).
What do you do if your MCU is 5V or 3.3V ? This is a commonplace need and there are jellybean parts for this, not in short supply or specialty items. I also use a BJT to drive a relay for example with 3.3V MCU's.
 

Papabravo

Joined Feb 24, 2006
19,023
The 2N7000 is older (30 years) through-hole TO-92 and people have moved on to SOT-23. MOSFET technology did greatly improve since then - lower VGS (on) and RDS (on).
What do you do if your MCU is 5V or 3.3V ?
...
You use a bootstrap circuit to produce an adequate gate voltage to turn on a garden variety FET and achieve a low Rds(on).
 
Ahhh it was Siliconix marketing that coined the term. I think of a Darlington as two semiconductors, in my world.

The VN10K and 2N7000 are extremely susceptible to ESD. I had many production problems with the devices soft failing G-S leakage or short, usually 1-2 weeks after. One company had them short leaving a fuel solenoid stuck on and a few explosions. Even had Vishay do SEM failure analysis on them. If you want to know if your manufacturing is proper ESD protected, make a test board with those mosfets on them and see if they survive. Really.
I think in the end, the PC board mounted on a plastic door that users could open, their fingers/gloves must have arc'd to the board where the mosfets were located. Or our manufacturing was just sloppy with ESD straps etc. and boards got micro discharges during handling. Techs replacing boards with parts also had failures after about 1 week. Predictable.
The gate junction is so small, they seem to not take much charge to induce HV gate failures.

TBH now I do not use these parts without a gate zener, lesson learned. i.e BSS138K
 

MaxHeadRoom

Joined Jul 18, 2013
25,669
I do/did make up many custom boards for systems I installed in industrial environments, so much easier and quicker to use thro-hole technology.
I have never recalled ever repairing replacing any of the many 2n7000 I have used over the years.
Recently I have been using them in Microchip applications , no problems.
 
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