When you buy from Digikey, you pay a significant premium for service -- they have a HUGE selection, they have the overwhelming majority of them in stock, they ship most orders the same day, the parts are brand new, you can pretty much count on them NOT being counterfeit, and they are willing to sell you just one of them. Those factors are worth a LOT to engineer.

Ditto for Mouser!

 

Not as big of slection os some sites mentioned but i use http://www.futurlec.com/index.shtml when ordering parts. they have treated me well. also i find transistors alot cheaper there.

 

hiiiii
i have received the cheap mosfet irlz44n...the mosfet not opening with 3.3v on gate at all !! is it fake mosfet?

 

You need more voltage.

 

You need more voltage.

why? it is logic mosfet and in datasheet if the gate-source =3v the drain-source 20A ..right?

 

Sorry I thought you wrote irfz44 which is a power mosfet.Did you test it out with a DMM?Do you have the schematics?

 

Sorry I thought you wrote irfz44 which is a power mosfet.Did you test it out with a DMM?Do you have the schematics?

***Drain-Source = 5v

@ 3.3v on gate ...i get 0A ...no thing

@ 4.2v on gate ...i get 5A & the mosfet get hot quick

@ 5v on gate ... i get 11A (full load) & the mosfet cool

 

The only thing the datasheet seems to guarantee is that at 2.0 volts Vgs, there will be at least 250 uA of current. The other curves are typical, and not guaranteed. That said, it looks like you might have counterfeit or reject devices.

 

***Drain-Source = 5v

@ 3.3v on gate ...i get 0A ...no thing

@ 4.2v on gate ...i get 5A & the mosfet get hot quick

@ 5v on gate ... i get 11A (full load) & the mosfet cool

Do you have the circuit?
What is the load, and how many ohms?

 

Do you have the circuit?
What is the load, and how many ohms?

the load 500mohm Nichrome wire

my setup ... 5v __load__Drain__Source__Ground

 

the load 500mohm Nichrome wire

my setup ... 5v __load__Drain__Source__Ground

IRFZ44N info:
VGS(TO), Gate threshold voltage, VDS = VGS; ID = 1 mA, 2.0V(min), 3.0V(typ), 4.0 V(max)

So if your Vgs of mosfet >3.3V then when you input 3.3V to Vgs then it has no current flows through the Ids.

Vdd = 5V
RL = 0.5Ω

Ids = Vdd/RL
= 5V/0.5Ω
=10A

The above calculation is ignore the Vds(When mosfet is on) and the problem is when the Max Ids is 10A then how can you get 11A? (Is it when the RL getting hot and the resistance decreasing?)

 

@ 5v on gate ... i get 11A (full load) & the mosfet cool

There you are, then. It's working with a logic-level Vgs, like it says on the tin .

 

IRFZ44N info:
VGS(TO), Gate threshold voltage, VDS = VGS; ID = 1 mA, 2.0V(min), 3.0V(typ), 4.0 V(max)

So if your Vgs of mosfet >3.3V then when you input 3.3V to Vgs then it has no current flows through the Ids.

Vdd = 5V
RL = 0.5Ω

Ids = Vdd/RL
= 5V/0.5Ω
=10A

The above calculation is ignore the Vds(When mosfet is on) and the problem is when the Max Ids is 10A then how can you get 11A? (Is it when the RL getting hot and the resistance decreasing?)

i have irlz44n not irfz44n...so?

the load about 300mohm..not exact

 

Hello,

@ScottWang ,

You are mixing the numbers.
Here is the data of BOTH mosfets:





You can see that the Vth of the IRLZ is lower as the IRFZ

Bertus

 

Hello,

@ScottWang ,

You are mixing the numbers.
Here is the data of BOTH mosfets:

View attachment 102286

View attachment 102287

You can see that the Vth of the IRLZ is lower as the IRFZ

Bertus

Thanks bertus.

 

i have irlz44n not irfz44n...so?

the load about 300mohm..not exact

The IRLZ44N infos:
VGS(th), Gate Threshold Voltage, 1.0(min) -–xx(typ)–– 2.0 V(max), VDS = VGS, ID = 250μA

If your Vgs of mosfet 1V<Vgs<2V then when you input 3.3V to Vgs, it should has current flows through the Ids.

Vdd = 5V
RL = 0.3Ω

Ids = Vdd/RL
= 5V/0.3Ω
=16.67A

>@ 3.3v on gate ...i get 0A ...no thing
The 3.3Vin for Vgs already exceed the Max Vgs(th)=2V, So this could be some problem here.
And the other make sense now.

 

Hello,

Could you post a schematic of your setup?

Bertus

 

Hello,

Could you post a schematic of your setup?

Bertus

 

The IRLZ44N infos:
VGS(th), Gate Threshold Voltage, 1.0(min) -–xx(typ)–– 2.0 V(max), VDS = VGS, ID = 250μA

If your Vgs of mosfet 1V<Vgs<2V then when you input 3.3V to Vgs, it should has current flows through the Ids.

Vdd = 5V
RL = 0.3Ω

Ids = Vdd/RL
= 5V/0.3Ω
=16.67A

>@ 3.3v on gate ...i get 0A ...no thing
The 3.3Vin for Vgs already exceed the Max Vgs(th)=2V, So this could be some problem here.
And the other make sense now.

i thing you misunderstand Vgs(th)...if Vgs(th) =2v then the mosfet will pass 250uA..so for turn off fully Vgs must be under about 2V...and to turn on fully (more than 250uA) vgs must be more 2v

 

i thing you misunderstand Vgs(th)...if Vgs(th) =2v then the mosfet will pass 250uA..so for turn off fully Vgs must be under about 2V

No, I didn't.
The Vgs(th) of mosfet is 1V<Vgs(th)<2V, that is depends on what you get of the mosfet, maybe the one you get the Vgs(th) = 1.1V, maybe it is Vgs(th) = 1.9V, so when you input 3.3V for the Vgs of mosfet then you should get the reading numbers exceed 250uA from the current meter, but you said no current, that's why I said there were some problems at some where.

If your Vgs(th) of mosfet is 1.1V then the turn off voltage will be <1.1V, if your Vgs(th) of mosfet is 1.9V then the turn off voltage will be <1.9V.