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Topic: Buying Transistor (Read 239 times) previous topic - next topic

jackrussell

Hey I need to get a transistor that can be triggered by pins on the arduino micro. It needs to allow at least 15 amps and 30 volts across the collector and emitter. I bought a TIP3055 but I do not think that the arduino can apply enough amps to power the base (correct me if I am wrong). What transistors can I buy that can do this, or how can search for them?

dannable

Years ago, when Moses was a lad, I used to use a BC107 to drive a 2N3055, creating what in effect is a Darlington pair.
Beginners guide to using the Seeedstudio SIM900 GPRS/GSM Shield

Peter_n

Hi, welcome to the forum.

Transistors are so 1980's. We are now in the mosfet era.
For a one or two amps, sometimes a darlington transistor is used, but mosfets are more fun.

https://www.sparkfun.com/products/10213
Even though that one is 30A, and you need only 15A, that is still a lot. You could put 3 of them parallel.

Do you need high frequency switching ? Those high current mosfets are not very good at high frequencies, because the gate is like a capacitor that has to be charged and decharged.

Paul__B

You do not use Darlington transistors for high current switching as they do not "turn on" sufficiently.

MarkT

#4
Aug 14, 2015, 12:40 am Last Edit: Aug 14, 2015, 12:42 am by MarkT
The way to choose an appropriate MOSFET is to go by the Rds(on) resistance, not the
current rating.

Determine the maximum power you want to dissipate and choose Rds(on) low enough
to ensure the dissipation is not exceeded (I-squared-R).

Also check that the maximum voltage across the device when on is low enough (much
less than the gate-source voltage, certainly less than a volt).

If you get a 10A MOSFET and put 10A through it that means you are at its thermal
limit with infinite heatsink - you don't want to be driving it anything like that hard.

For 15A continuous I'd be choosing something with an on resistance of 3 milliohms
or less.

These days a power BJT like the 2N3055 is a museum piece - it only has a usable
switching gain of about 5, you'd typically have a driver transistor and a pre-driver
as well.   All replaced these days by one MOSFET with 100 times faster switching
if driven properly.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

JoeN

IRL540?  Use a 200 ohm resistor to drive the base.  If you need to drive it quickly, like for a fast PWM, use a MOSFET gate driver IC.

http://www.digikey.com/product-detail/en/IRL540PBF/IRL540PBF-ND/812025

Datasheets   IRL540
FET Type   MOSFET N-Channel, Metal Oxide
FET Feature   Logic Level Gate
Drain to Source Voltage (Vdss)   100V
Current - Continuous Drain (Id) @ 25°C   28A (Tc)
Rds On (Max) @ Id, Vgs   77 mOhm @ 17A, 5V
Vgs(th) (Max) @ Id   2V @ 250µA
Gate Charge (Qg) @ Vgs   64nC @ 5V
Input Capacitance (Ciss) @ Vds   2200pF @ 25V
Power - Max   150W
Package / Case   TO-220-3
I will never ask you to do anything that I wouldn't do myself.

TomGeorge

Hi,
What is the load you want to control?
Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

MarkT

#7
Aug 14, 2015, 06:42 pm Last Edit: Aug 14, 2015, 06:44 pm by MarkT
IRL540?  Use a 200 ohm resistor to drive the base.  If you need to drive it quickly, like for a fast PWM, use a MOSFET gate driver IC.
No, no good for 15A, as I said 3 milliohm would be good, perhaps 10 milliohm at a pinch with
reasonable heatsink, but 77 milliohm too high.

For the performance needed a logic-level MOSFET might be hard to find, but mosfet drivers are
cheap plentiful and a good idea in the first place for high power switching.

An example of a possible device is IRLS3036, 60V, 1.9 milliohm, logic level.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

JoeN

An example of a possible device is IRLS3036, 60V, 1.9 milliohm, logic level.
I had problems finding anything that had low Rds(on), was logic level, and was through hole.  This is a really nice device.  Only complaint many people will have is that it is a surface mount device.  Also, so very expensive.  Still, looks like this guy will sell you one or two very inexpensively, shipping included at least in the US:

http://www.ebay.com/itm/MOSFET-IRLS3036-7PPBF-N-CH-60V-240A-D2PAK-/221196773624
I will never ask you to do anything that I wouldn't do myself.

CrossRoads

Logic level, Low Rds, Low Gate capacitance, thru hole N-channel MOSFET, 50 cents, that I use a lot:
http://www.digikey.com/product-search/en?keywords=aoi514

You can see 32 of them on this board that I offer:
http://www.crossroadsfencing.com/BobuinoRev17/

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

JoeN

Logic level, Low Rds, Low Gate capacitance, thru hole N-channel MOSFET, 50 cents, that I use a lot:
http://www.digikey.com/product-search/en?keywords=aoi514
That looks like a really nice part.  I will have to buy a few on my next Digikey order.  The Rds value is a little higher than MarkT wants, but that's the best I have seen for "fairly" low Rds, logic level, through hole, and very reasonable price.
I will never ask you to do anything that I wouldn't do myself.

Chagrin

The TO-220 part is the IRLSL3036PbF. It's almost $5/each (Qty 1) though.

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