I bought a couple of MOSFETS, Philips BUK100-50GL, overkill I know (for my current requirements) but easily available from the Farnell catalogue. I haven't found data sheets or application notes yet, but they are driveable from TTL which sounded attractive. ;-) It's a TO220 package with the pins labelled (top view looking down) i/p, d, s. I've experimented with a 0k, 10k and 100k resistor connected from source to i/p, +5V on the source (source voltage) and drain going to target Vcc control. I find I get 4.5V out when the i/p is floating or tied to Gnd or tied to +5V, in all the above except with the 10k resistor where the output fell to about 4.1V. Anyone mind telling me what I'm doing "wrong"?! Or any alternatives for controlling two 5V devices from digital TTL (or 5V and 3.3V later) which take around 500mA (5V), and around 300mA (3V) - but with very short 2A peaks (GSM when transmitting). Regards Adrian --- WWW WWW Adrian Gothard WWW WW WWW White Horse Design WWWWWWWWWW +44-385-970009 (Mobile/SMS), +44-118-962-8913/4 (voice/fax) WWWW WWWW whd@zetnet.co.uk, http://www.users.zetnet.co.uk/whd --- Developers of GPS satellite-based tracking systems for vehicles/helicopters