MOSFET choice?

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Nix

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Hi

I wonder if anyone can advise me on choosing the right component?

I need a component to act as a high-side switch to send a 6v pulse to a solenoid rated at 450mA.

I am using 3.3v logic, and low power consumption is a priority.

I figure the ideal would be a P-MOSFET which is above saturation at 3v or so.
In the final application, the pulse will only be 100msec, but while I am still testing, I'd be happier if the component could happily dissipate 4watts for a few tens of seconds.

I am having difficulty identifying a suitable part as I am pretty inexperienced.

Any advice would be much appreciated

Thanks

Phil
 
FOR THIS APPLICATION a TO5 can is sufficient 4 ms pulse is not much now here is the thing if the pulse is repeated withing 10ns then you will have problem is on all the time. fet have ohmic value when saturated for 450ma any kind will suffice.
 
Thanks, Ill look for a p-mosfet with TO5 case. That narrows my search a bit. I am finding that there are plenty of p-mosfets that will handle 450mA continuously with a gate-source voltage of -5v, but not -3v, which is what I am using. Maybe I am not reading datasheets correctly. If you can mention a particular part, that would help me make more sense of the datasheets.

Many thanks

Phil
 
Thanks
This looks interesting - Ive not seen one of those components you recommended. Farnell don't have them, but I will look for more recent similar products. I just figured that of the 4000 or so mosfets that farnell stock, there would be a fair few that would do the job. I guess I could always use a PNP power transistor, but I do like the efficiency of MOSFETs.

Cheers

Phil
 
Since similar parts have different numbers in different markets, you would help us to help you by filling in your location (continent at least) in your user profile.
 
Finding a MOSFET that will pass 450mA with a gate voltage of just 3.3V isn't easy. Pay attention to the threshold voltage and check the datasheet to see it it can supply the current you require at the gate voltage you provide.
 
Irlml2402? That is my "stock" FET I use for something like this. It's N-channel though.
 
Last edited:
Hi
Thanks for the tips. I havent found the perfect device yet, so I have tried something else; I really need the fet to act as a high side switch so in the end, rather than look for a single device that does all I want, I have decided to go with a P channel power mosfet which I drive with a smaller logic level N channel fet.
Thanks,

Phil
 
Digi-Key - FDN306PCT-ND (Fairchild Semiconductor - FDN306P)
I am afraid most LVCMOS drive FETs will be SMT. There are actually a number of ways to drive it...an NPN with the base resister to the 3.3V rail comes to mind.
 
That looks perfect.

Don't worry about it being SMT - they're pretty easy to use, even on veroboard.
 
Thanks - I figured I may as well try surface mount parts. In the end I used a tiny N mosfet - a 2N7000, SOT 23. I have been using blu-tak to hold smd parts in place while I solder the first leg. Seems to work ok.
cheers

phil
 
Nix said:
Thanks - I figured I may as well try surface mount parts. In the end I used a tiny N mosfet - a 2N7000, SOT 23. I have been using blu-tak to hold smd parts in place while I solder the first leg. Seems to work ok.
cheers

phil
Click to expand...
Please post a schematic of the circuit you used.
 
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