2 ampere mosfet selection help

i want to switch load of 2amp (GSM modem) can any one advice any mosfet to use, preferably smd one.
for some reason gsm modem is not responding to off key so i have to cut its power supply.
i am using 3.3v pic and gsm modem needs about 4.2v

thanks

with the voltage levels / and low current of a uC you are using it is not possible to switch ON/OFF a mosfet in proper manner ( you might be working in the linear (triod region) were the mosfet is amplifier not switch and switching losses are higher .
and why do you need a MOSFET , if i were you i would use a BJT , probably a darlington ... if you want i can suggest few ( SMD ones offcourse )

hope that helps !;-)

Electro nS said:

with the voltage levels / and low current of a uC you are using it is not possible to switch ON/OFF a mosfet in proper manner ( you might be working in the linear (triod region) were the mosfet is amplifier not switch and switching losses are higher .
and why do you need a MOSFET , if i were you i would use a BJT , probably a darlington ... if you want i can suggest few ( SMD ones offcourse )

hope that helps !;-)

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thank you for your reply.
yes please suggest SMD BJT
I tried using 2N2222A transistor, i can cut power supply but when modem tries to attach to network it restarts because 2N2222A cannot provide 2amp peak current.

i want to switch load of 2amp (GSM modem) can any one advice any mosfet to use, preferably smd one.
for some reason gsm modem is not responding to off key so i have to cut its power supply.
i am using 3.3v pic and gsm modem needs about 4.2v

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Hi devil6600
You've many ways for going through . for mosfet , there are gang of mosfets available . for instance IRFZ44 or something like that . by the way you've noticed that you're using PIC for it's command and your Command signal has a rating around 3.3 volt , so you can go though some kind of logic level mosfets . you can easily go through www.irf.com and select your desired one .
You can also use some high power opto couplers too . ( with totem pole in out put , internally ) . another option is BJT as Electro nS mentioned before , but a darlington pair .

2N2222A cannot provide 2amp peak current.

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Of course it can't because of two reasons :
1- it is designed for low powers .
2- it's beta isn't sufficient for your aim .
you can try TIP series like TIP 102 .

Best Wishes
Goldsmith

devil6600 said:

thank you for your reply.
yes please suggest SMD BJT
I tried using 2N2222A transistor, i can cut power supply but when modem tries to attach to network it restarts because 2N2222A cannot provide 2amp peak current.

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MJD122 , check out the data sheet
www.taitroncomponents.com/catalog/Datasheet/MJD122.pdf

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The tip 120 series are also good , but i am not sure if they are SMD
check these out they are more than enough for your application
MJD122
STD901T
NJD35N04T4G

devil6600 said:

and gsm modem needs about 4.2v

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Electro nS said:

MJD122 , check out the data sheet
www.taitroncomponents.com/catalog/Datasheet/MJD122.pdf

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The Vce saturation voltage drop may cause problems if the power supply voltage is close to the needed 4.2v and there is not enough headroom