Hi Matko123, You need to tell the community about your application is before it is possible to offer any advice. For example, What is the maximum current that the device will have to conduct in your application? What is the maximum gate current that is available to turn the device on and off in your application? What is the maximum drain-source voltage that will appear across the device in your application? What are the maximum and minimum gate-source voltages that will be presented to the device in your application? How fast are you turning the device on and off? :)

BTW, both parts exist in the library and physical parts can be supplied by EasyEDA.

Sorry, but i dont know. I am not begginer. I want only your idea. I am asking for normal projects. So, for example watch this project: http://www.instructables.com/id/DIY-Boost-Converter-How-to-Step-Up-DC-Voltage-Effi/

`Sorry, but i dont know.` Then you must make the effort to find out. `I am not begginer.` All the more reason that you must find out more about your application before trying to swap components about. `I am asking for normal projects` But what is a `normal` project? Are you turning a relay on and off once a day in an exterior night light? Are you building a 1kW 1MHz Boost Converter? A 30V 20A Linear Bench Supply? These all require different considerations in order to decide if one device could safely be substituted for another. * Without specific information about your application it is not possible to say with any certainty if you can use the devices interchangeably. * Under those circumstances, it could quite easily be dangerous for anyone to do so without the relevant information. If you answer the questions that I listed in my earlier post above and compare the specifications for each of the devices: http://www.irf.com/product-info/datasheets/data/irlz34n.pdf http://www.irf.com/product-info/datasheets/data/irlz44n.pdf then you should be able to decide for yourself if you can use the IRLZ34N in place of the IRLZ44N in whatever the application is that you wish to use the devices.

Thanks. So, in the last : can i use IRFZ44 instead of IRLZ44?

`...can i use IRFZ44 instead of IRLZ44?` Sorry but they are not equivalents so the same answer applies.

Aha

If you want to understand switched mode power supplies and how to design them properly tyhen you could study these: http://www.onsemi.com/pub/Collateral/SMPSRM-D.PDF http://www.smps.us/Unitrode.html Better still, if you have the money, get a copy of Christophe Basso's excellent book on Switched Mode Power Supply Design and Simulation (now in 2nd edition): cbasso.pagesperso-orange.fr/Spice.htm There is a lot of other useful info on this page. If you install a copy of the free LTspice simulator: http://www.linear.com/designtools/software/#LTspice (Runs natively on OSX and Windows and using WINE on Linux) then you can look in detail at the behaviour and governing equations of the basic Boost and Buck SMPS topologies by dowloading the simulations from here: https://drive.google.com/file/d/0B2wonnsWWfTXY3NIdUhMWFktOVU/view?usp=sharing https://drive.google.com/file/d/0B2wonnsWWfTXZmlxSk9pbjFZZEU/view?usp=sharing There are some more simulations here on EasyEDA: https://easyeda.com/andyfierman/Misc_simulations-lVd6oGYSa