Need higher speed 2N7002

Well, I do simple RC ramps, no feedback, much simpler, and get 3 ps jitters.

This is a common pattern: a governmant employee uses government time and government lawyers to accumulate a stable of inane patents. Then, reputation assured "...holder of over 32 US and foreign patents..." he splits, starts up a company, licenses his own useless patents from the Regents, and raises a bunch of angel and VC money on the strength of his "exclusive" patent portfolio. I've seen that many times.

John

Most of the 10X driving solutions, (cascode, parallel gate inductor, shove more current into the gate, reduce wiring inductance or look for a fast reels or better manufactor of the 2N7002) were not viable solutions either because not enough speed increase or too many parts. Win H. points out that the lowest Ron may not be best for every application, we must optimize the other parameters. The 2N7002 is not optimal for 20MHz switching. With all the MOSFET improvements we have seen in the last 20 years since the 2N7002 made it's début, you would think that someone would manufactor a device with the same gate voltage thresholds, drain voltage, Ron but less parasitic capacity enabling higher speeds. A X10 cost increase would be palatable. My application, transcutaneous power/data transmission has very limited space and GaAsFETs require too many components and is way overkill in speed. Cheers, Harry

>

So what happened to due diligence on the part of the VC folks? Before our company bought or invested a single dime we turned everything upside down, seeking 2nd, 3rd, 4th opinions from experts and so on. Not a stone was left unturned. Then we returned to HQ and sorted what we found into three categories, "really need that", "may be worthwhile" and "hot air".

--
Regards, Joerg

http://www.analogconsultants.com

You can drive a 3-cent 2N7002 from a 15-cent TinyLogic gate and get a couple-ns switching speed at 60 volts drain swing. What's not to like about that?

John

Do you remember when the company was called "Galvin Manufacturing"? Do you know where the "Motorola" name came from? Do you remember an early PC that ran CPM that was forced to change their name from Galvin by Motorola?

--
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

I joined Motorola in 1962, so it was no longer "Galvin Manufacturing", but we were regularly indoctrinated with the company history ;-)

I think (but am unsure) it came from car radio manufacture in their home garage.

Nope. Never heard that one.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

The 15c for the TinyLogic. It's kind of highish...

--
Regards, Joerg

http://www.analogconsultants.com

Well, that's in hundreds. NL37WZ16US triple buffer. Use all three sections in parallel and power it from 6 volts. It'll slam 5 volts into 50 ohms in about 600 ps, and bash a 2N7002 gate right proper.

That sort of performance is almost worth the miserable US8 package.

John

. snipped-for-privacy@j27g2000cwj.googlegroups.com...

But John Jardine posted earlier: "I've had 1nS using a 15V supply,

50ohm load and driven direct from 74AC (5V) logic."

That's fast, and pretty simple (if you have such an output). (We don't know what you have.)

True. If you really need the low Rds(on), I didn't see many better choices--you need a larger FET, and it's gonna take some driving.

If you can stand Vds(br) of just 25V and Rds(on) =3D 5 ohms(max) @ Vgs=3D2.7v, Fairchild's FDV301 might merit a gander.

FDV301: Ciss(typ) =3D 9.5pF, Crss(typ) is only 1.3pF, which should make it much easier to drive quickly.

2n7002: Ciss(typ) =3D 20pF, Crss(typ) 4pF. (Fairchild)

That depends on how much power you're switching and your effciency requirements, of course. ISTM from a few 10s to 100s of mA it could be great.

that

X10

Maybe you'd think that, but I checked OnSemi, NXP, Supertex, Zetex, Infineon, and Fairchild, and couldn't do any better.

ed.

Best, James Arthur

One of my gadgets uses a CLY2 mesfet (source follower) to drive two

2N7002's in parallel, 12 volts of gate drive in about 400 ps. That works pretty good, although turnoff is slow with a passive gate pulldown.

If you use tinylogic as gate drivers, just use a driver per fet and connect all the drains.

You can't get extreme performance without doing stupid things.

John

It will turn on in a couple-ns but toff depends on Coss which is about 20pF for a 2N7002. For less than 5nS rise times you need

But John Jardine posted earlier: "I've had 1nS using a 15V supply,

50ohm load and driven direct from 74AC (5V) logic."

That's fast, and pretty simple (if you have such an output). (We don't know what you have.)

True. If you really need the low Rds(on), I didn't see many better choices--you need a larger FET, and it's gonna take some driving.

If you can stand Vds(br) of just 25V and Rds(on) = 5 ohms(max) @ Vgs=2.7v, Fairchild's FDV301 might merit a gander.

FDV301: Ciss(typ) = 9.5pF, Crss(typ) is only 1.3pF, which should make it much easier to drive quickly.

2n7002: Ciss(typ) = 20pF, Crss(typ) 4pF. (Fairchild)

That depends on how much power you're switching and your effciency requirements, of course. ISTM from a few 10s to 100s of mA it could be great.

Maybe you'd think that, but I checked OnSemi, NXP, Supertex, Zetex, Infineon, and Fairchild, and couldn't do any better.

Best, James Arthur

That FDV301N looks like the best I've seen, Coss at 6pF is 3X better than the 2N7002. Thanks for all your help. Harry

Nanosecond-speed, high-impedance signals basically don't exist in nature, and what would you do with them anyhow? You can do a little better with a gaasfet, 400 mA drive with maybe 3 pF of drain capacitance, up to maybe 10 volts, for a few bucks.

Sounds to me like you're determined to not be satisfied.

Oh, I wasn't suggesting cascode from the tinylogic, just simple gate drive.

John

John I am satisfied in knowing that with yours and other peoples help we have searched for faster low power FETs and the Fairchild FDV301N is about the best we can find in a small package, readily available at a reasonable price. Fairchild has the FD301N, FDV302P, FD303N, FD304P and FD305N. The N and P mean just what you think. The help in making the 2N7002 faster was not needed but other readers may have learned something. That makes me very happy that I can now move on to bigger and better things. Thanks for all your past and future help. Harry

Most VCs don't care about technology or viability, they care about fads, and their vision ends at IPO. Buy it, hype it, sell it off. The dot.com thing worked that way, and they gave it a good try in nanotechnology, with less success.

John

That doesn't really work in medical electronics. At least not anymore. Most of the time the goal is not an IPO but a take-over by one of the large pharmaceutical companies in a cash or stock transaction. Even if an IPO is contemplated that again hinges on acceptance of the underlying technology by large med companies. If that interest doesn't materialize the whole thing fizzles, usually.

I am sometimes involved in such processes and nowadays everyone is really working hard to build truly useful IP. Meaning that funding will only happen if you can make a very good case and convince the VC that there is a significant chance that it's going to fly.

--
Regards, Joerg

http://www.analogconsultants.com

I'll have to try those. It seems that all the new lithography is going into lower-voltage parts (fets, opamps, fpga's, everything) so if you need 50 volts, an ancient 2N7002 is about as good as it gets, unless you can spend $50 or so on GaN.

Of course, we don't know what the *actual* breakdown voltage is on the FDV301!

John