In this site, third paragraph, they said the BS270 is designed for logic level input.

In the datasheet I could not find anything suggesting that.

Is it or it isn't?

 

Here is the Data Sheet...

http://www.fairchildsemi.com/ds/BS/BS270.pdf

I think it is, but the data sheet is unusual in that it does not come out and say so directly. Usually this is a selling feature, so I am a bit uncertain.

One thing though, data sheets are always your friend.

 

The data sheet calls out the Gate Threshold Voltage when VDS = VGS, ID = 250 μA to be a min of 1 volt and a max of 2.5 volts.

Yes, that makes it a logic level FET.

 

The BS270 looks very similar to the 2N7000 datasheet, only better power handling characteristics, definitely logic level. Also, the pinout is reversed from the 2N7000.

 

It is logic level, but I'll ask everyone else this just for the OP's reference:

Should he be concerned that Rds(on) is not specified for any Vgs below 4.5V (if he were considering using 3.3V to turn it on)?

 

It is logic level, but I'll ask everyone else this just for the OP's reference:

Should he be concerned that Rds(on) is not specified for any Vgs below 4.5V (if he were considering using 3.3V to turn it on)?

From the data sheet I would say it works ok for 5V logic but not for 3.3V logic, which is barely above the threshold voltage.

 

When its gate-source voltage is logic-level at 4.5V:
1) Its maximum on-resistance is 3 ohms.
2) Its drain-source voltage drop is 2V when its current is at least 400mA.

Is that good enough for your circuit?

 

When its gate-source voltage is logic-level at 4.5V:
1) Its maximum on-resistance is 3 ohms.
2) Its drain-source voltage drop is 2V when its current is at least 400mA.

Is that good enough for your circuit?

I have no circuit in mind AG.

I realize that maybe, in 1995 there were not so many logic level MOSFETS, at least described as such...

Thanks to all replying.