Can you please tell me how can I tell in a parts catalog which mosfets are depletion type and which are enhancement type? Do these have some other names?

Can you give me some examples of those transistors? For example IRFP240 is what?

 

Datasheets are available on the web for download. Here's an example:
http://www.ortodoxism.ro/datasheets/fairchild/IRFP240.pdf

Simply typine the part number into Google is usually good enough to find a datasheet. See the "resources" forum here for some collections of datasheets.

 

From a circuit schematic perspective the difference is identified by on of two methods:

1) The channel for the depletion-type MOSFET is a bolder line than for an enhancement-type. This notation is widely used in CMOS schematics and literature and is the one I am most accustomed to.

2) The channel for the depletion-type is a continuous line, whereas for an enhancement-type it is a dashed line. For an example of this notation refer to the relevant section in All About Circuits Volume 5:Chapter 9.

Edit: Have I misread your question?

Dave

 

Of course I can find the datasheet for each transistor, but I wanted some more general rule to identify them just by the part name, if such a rule exists.

When I read through a paper parts catalog, I can´t type each transistor in explorer and read the datasheet.

 

There is generally no connection between part numbers and device parameters. Many companies start out with proprietary designs, build them for a while, and then license them to other manufacturers. In the case of the IRFxxxx parts they were originally done by a company called International Rectifier.

At one time there may have been a scheme among the 1N diodes, and the 2N transistors, but if there was it broke down a long time ago, perhaps in the early 1970's

Fairchild and On Semiconductor may encode some parametric information into the more modern parts but when I'm looking for a part I use the online selection guides.

 

And is here some online selection guide not only for company products, but for example for most of the transistors which are currently available on market?

 

It seems as though I have misinterpreted the original question. Transistor makrings tend to follow one of several standards for indentification, however there is no way of indentifying the channel-type from the part number in JEDEC or Pro-Electron standards. I do remember the JIS standard which differentiated between n-channel and p-channel devices through use of a sequence of letter, IIRC the format was something along the lines of:

<Component Number><Component Type><ID Numbers>

Where the component type would be used to identify the FET channel-type.

I can try and dig out some info if it would help.

As for IRFP240, try here.

Dave

 

Can you tell me just one depletion type N mosfet? I have a feeling the depletion types are harder to find, aren´t they?

 

Try the FT57 though it is now discontinued. You will find JFETs are much more useful/more widely used, devices when operated in depletion mode.

Dave

 

There are many active depletion-mode power MOSFETs. Most of these are used in medium to high voltage power application due to their unique characteristics and also many end up in solid state relays. Have a look at Ixys or Supertex MOSFETs.