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Author Topic: Req: cheap/common mosfet for 3A - 10A  (Read 4131 times)
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iphone
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« on: October 02, 2010, 09:59:56 09:59 »

hi guys.

Anyone knows what's mosfet (spec no.) which can supply between 3A - 10A (I mean a few mosfet which can deliver/supply (use as a switch) for 3A, 5A and 10A).

The reason is, normally if I want transistor to deliver 5A ( as a switch) , I used TIP127 and TIP122 (NPN n PNP) but this is high cost and big package T0 220.

So my point is, anyone know any mosfet spec can do switching for 5A and it cheap/common/easy get component? how about 3A and 10A ?

if possible, the mosfet package is same as transistor BC547/2n3904 .

tq
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« Reply #1 on: October 02, 2010, 11:18:59 11:18 »

try

STMICROELECTRONICS - STD30NF06T4

http://uk.farnell.com/stmicroelectronics/std30nf06t4/mosfet-n-ch-60v-28a-dpak/dp/1752033

it has a vgsmax of 4v

---------------------------------------------------------------
this IR has a vgsmax of 2V, so can be driven directly from a micro
INTERNATIONAL RECTIFIER - IRLU3410PBF

http://uk.farnell.com/international-rectifier/irlu3410pbf/mosfet-n-100v-15a-i-pak/dp/8660280


----------------------------------------------

just an additional point, always look at the curves of Drain current Id vs voltage VDS, the VGSmax is just the guaranteed voltage to turn on the mosfet with 1 mAmp or so. to deliver amps, you need to drive the gate hard, so the IR mosfet needs 4 volts to give 10Amps, and even then, its dropping 1.5 volts, so dissipating 15watts !!!!

Mike
« Last Edit: October 02, 2010, 11:30:29 11:30 by Old_but_Alive » Logged
iphone
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« Reply #2 on: October 03, 2010, 06:05:35 18:05 »

Code:
so the IR mosfet needs 4 volts to give 10Amps, and even then, its dropping 1.5 volts, so dissipating 15watts !!!!

Can you explain more please.

As I know, for switching mosfet normally cooler compare to normal transistor.

I drive mosfet using op-amp such as LM358.

tq
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« Reply #3 on: October 03, 2010, 08:13:54 20:13 »

if you look at the datasheet, and the graphs of IDS vs VDS, for the various gate drive voltages VGS, you will see that when IDS is say 10Amps, then the VDS will be 1Volt to say 4 volts, depending upon VGS.

so, if the current is 10, and the VDS is say 1.5V, then power = I x V = 10 x 1.5 = 15 watts.


the key selection with mosfets is Ron, VGS, and VDbreakdown.

that IR device has quite a high Ron of 100mOhms, so a better mosfet would have say 20mOhms, but then you would need quite a high VGS to drive it.

even a normal bipolar transistor delivering 10 Amps will have a volt or more across emitter-collector, so will again be getting hot

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« Reply #4 on: October 03, 2010, 10:55:12 22:55 »

For a 12V Gel Cell powered portable project I'm soldering on now I selected an
AO3416 FET.  The FET controls a small DC motor which draws 2 amps. 

AO3416 spec's are as follows:

   SOT-23 package.
   VDS = 20V
   ID = 6.5 A
   RDS(ON) < 22mΩ (VGS = 4.5V)

   DATASHEET HERE

Cost is only $0.15 each in 1000 lots from Digikey.
A mighty amazing little chunk of silicon.   Cool



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« Reply #5 on: October 04, 2010, 10:18:32 10:18 »

@oldvan,

cant argue with the price, or the specs,... a good find.

It wont do the 10Amps, but I suppose one could put 2 or 3 in parallel to get the 10Amps.

Never heard of Alpha and Omega semiconductor in all of my 40 years in the game.

just checked them out, they are American, but fabless.

founded in 2008.
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« Reply #6 on: October 08, 2010, 04:50:10 16:50 »

If you use the Popular part nos like IRF530, or IRF630 you will be able to get a very good price because they are used in millions. you will see that a larger rated mosfet which is populer will be available at a lower cost than even the low current non popular types.
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« Reply #7 on: October 08, 2010, 06:04:08 18:04 »

@Jehan,

not checked the price, but the 630 looks the better bet, but needs to be driven by Vgs of 10 volts
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« Reply #8 on: October 10, 2010, 09:47:41 09:47 »

If the voltage you have to switch isnt to high IRLB8748 might be an option.
(from the cost point of view ,also they have a rather small gatecharge making the driving easy)
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« Reply #9 on: October 10, 2010, 04:48:44 16:48 »

btw, for transistor to do the same job (5A - 10A), anyone know the cheap/common transistor part no?

I use TIP 127/122 n TIP147/142.

rgds
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« Reply #10 on: October 10, 2010, 06:55:31 18:55 »

I use a lot of IRF72xx & IRF73xx SMD 8pin IC type
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« Reply #11 on: October 13, 2010, 05:36:39 17:36 »

Zetex have very usefull parts eg.
http://www.diodes.com/datasheets/ZXTN19020DG.pdf
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« Reply #12 on: October 19, 2010, 04:07:18 04:07 »

I'm a big fan of FDS4672A.

11Amps
40Volts
13mOhm
SOIC-8 Narrow Body Package

Other FDS Series with varying Voltage/Current ratings that I use a lot..
FDS6670A
FDS6912A

All can be had for around a buck in qty of 1, and way less than that in higher qty.

PPtk
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« Reply #13 on: October 28, 2010, 09:25:07 09:25 »

Sparkfun have a new item, the RFP30N06LE for 95cents for 1 off.

its a T0220 so a leaded power package.

N-Channel MOSFET 60V 30A

sku: COM-10213

Description: If you've ever wondered how to control the headlight of a car from a microcontroller, a MOSFET is what you need. The RFP30N06LE is a very common MOSFET with very low on-resistance and a control voltage (aka gate voltage) that is compatible with any 3-5V microcontroller or mechanical switch. This allows you to control high-power devices with very low-power control mechanisms.
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« Reply #14 on: October 28, 2010, 06:50:30 18:50 »

Not always a transistor is cooler  than a mosfet,
it depends from the application

 Also ,LM358  is not the better solution in order to drive a mosfet
particularly for frequencies over the 10khz

Could you specify  application or what must drive  ?

 
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