FET's in series

George Herold · 2016-03-06T17:13:32+00:00

Hi all, This is a bit of a jibe on my Fet's as heater post back a while ago. In that thread (should I post a link?) Phil H, recommended FET's in series if I wanted to spread out the heat load. I was trying to figure out how that works. And (I think) copied from figure 9.111 of AoE3 (now at work.) But I left out a lot of the components,(caps and diodes etc.) Anyway the goal was to have about equal voltage drops across each of the FETs. (My first attempt was a failure.) Here's an LTspice file... I'm thinking my error might be the non-zero voltage at the source of the bottom FET. (I'm off to the HS musical so I won't be able to respond till later tonight.) TIA George H. Version 4 SHEET 1 944 680 WIRE 224 -272 -144 -272 WIRE 464 -272 224 -272 WIRE 224 -224 224 -272 WIRE -144 -176 -144 -272 WIRE 464 -160 464 -272 WIRE 224 -80 224 -144 WIRE 416 -80 224 -80 WIRE 224 -64 224 -80 WIRE -144 -48 -144 -96 WIRE 464 -32 464 -64 WIRE 464 -16 464 -32 WIRE 224 64 224 16 WIRE 416 64 224 64 WIRE -16 80 -240 80 WIRE 224 96 224 64 WIRE 464 160 464 80 WIRE -240 192 -240 160 WIRE 464 192 464 160 WIRE -16 208 -16 80 WIRE -48 224 -64 224 WIRE 224 224 224 176 WIRE 64 240 16 240 WIRE -48 256 -224 256 WIRE 64 272 64 240 WIRE 96 272 64 272 WIRE 416 272 176 272 WIRE 64 288 64 272 WIRE -224 368 -224 336 WIRE -64 368 -64 224 WIRE 64 368 64 352 WIRE 64 368 -64 368 WIRE 96 368 64 368 WIRE 464 368 464 288 WIRE 464 368 176 368 WIRE 464 384 464 368 WIRE 464 496 464 464 FLAG 464 496 0 FLAG 224 224 0 FLAG -16 272 0 FLAG -144 -48 0 FLAG -224 368 0 FLAG 464 160 D1 FLAG 464 -32 D2 FLAG -240 192 0 SYMBOL Opamps\LT1013 -16 176 R0 WINDOW 3 -117 12 Left 2 SYMATTR InstName U2 SYMBOL res 208 -240 R0 SYMATTR InstName R1 SYMATTR Value 1meg SYMBOL res 208 -80 R0 SYMATTR InstName R2 SYMATTR Value 1meg SYMBOL res 208 80 R0 SYMATTR InstName R3 SYMATTR Value 1meg SYMBOL nmos 416 192 R0 SYMATTR InstName M1 SYMATTR Value IRF530 SYMBOL res 448 368 R0 SYMATTR InstName R4 SYMATTR Value 1 SYMBOL cap 80 352...

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Jeroen Belleman 10 years ago

On 08/03/16 20:26, George Herold wrote: [...]

Tempter.

Jeroen Belleman

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John Larkin 10 years ago

Stud.

John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

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rickman 10 years ago

"God helps those who help themselves" and you can do a lot more for your business than the government ever could. Stop waiting for someone else to make "conditions" right for your business and just get on with it.

Rick

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Phil Hobbs 10 years ago

Is that a 2N7000E (no gate protection) ? The E series devices have recently been discontinued, and I've been debating with myself whether to buy a reel or two before they're all gone.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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John Larkin 10 years ago

I don't know. We have several sources listed as suppliers for 2N7000 and 7002. We don't use them in leakage-critical apps. The one that I pulled from stock had amazing gate leakage behavior, hours with little drift.

I also don't know what part Win tested for drain current.

John Larkin Highland Technology, Inc lunatic fringe electronics

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legg 10 years ago

2N7000, 2N7002 has (had) no gate protection.

RL

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Phil Hobbs 10 years ago

Depends on the model. Current production is all gate-protected AFAIK.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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legg 10 years ago

references?

RL

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John Larkin 10 years ago

I tried a 2N7000 from stock, Fairchild, which could be old. I got +100 volts on the gate without significant gate current, but a subsequent drain test suggests that I may have damaged something.

John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

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Phil Hobbs 10 years ago

You're right--looks it's just the Vishay ones that are gate protected. Guess I won't worry about it then. ;)

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net

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FET's in series

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