MOSFET substitution

[emtffkev]

I am fairly new to the world of building circuitboards and stepper controllers.

I am following some plans from PMinMO.com and it calls for some IRLZ44 MOSFET's. Now this may be just plain ignorance, but I have a whole BUNCH of TIP122's laying around and I was curious if I could use them instead?

[Al_The_Man]

These are used in PWM output's they are Darlington Drive transistors so different drive circuitry may be needed as the technology is a bit different to MosFet's in order to make sure they are turned full on in a H bridge mode.
Al.

[emtffkev]

Any suggestions on a 3 axis controller board that uses TIP122's? The only reason I ask is I have about 30 of them at my house, and I'm getting anxious to get my circuit built.

[Al_The_Man]

I know its nice to use item you have on hand, but at $1.50 each the proven Mosfet design maybe the way to go.
The mosfets have much lower on resistance and you have to make sure you switch the Darlingtons fast to avoid the linear region.
Al.

[emtffkev]

Ok, do you have any good suppliers for them? I found them at digikey, but they have a minimum order of 500 or something and I don't need that many at that price just to build one controller.

[Al_The_Man]

Digikey sell them for $2.00 in single quantity http://www.irf.com/product-info/data...irlz44npbf.pdf
You have to look at the stock items on hand.
Al.

[davesaudio]

try these part nums
IRLZ44NPBF-ND
IRLZ44ZPBF-ND

[NC Cams]

The IRLZ44's are VOLTAGE driven devices whereas the TIP's are CURRENT driven.

You can't simply swap one for the other without redoing the surrounding drivers for/to the transistors.

For best results, buy and use the listed parts - they are low voltage "logic level" devices that are quite counductive with only 5VDC and switch off and on fairly quickly. When properly driven, they'll conduct a lot of current and do so while remaining cool to the touch.

[tshatat]

thanks but did the IRFZ44 can replace the IRLZ44 and what the diference

[NC Cams]

Essentially, no.

Look at the Vgs curves for full enhancement voltage levels Between the two.

From our experience, the IRF needs nearly a Vgs of 15 to carry full current whereas the IRL version only needs 5 but works evne better at 10.

Regrdless of the version you use, USE A FET DRIVER. Do NOT drive directly from logic level IC's even though you theoretically can. Logic IC's can supply the voltage but not the current to saturate the capacitive load of the fet gates.