There are 4 type of mosfet’s SO8 on laptop motherboard 1. P channel mosfet 2.N chanel mosfet 3.dual P channel mosfet 4.Dual N chanel mosfet each type could substitute as long as same type even with different marking code. Easy way to identified look at the end number of marking code . example : AO 4433 look at end of marking code number is odd numbers ( 3 ) this is P channel example : AO 4407 (7) is odd number ,this is P channel too, they could be substitute each other even different manufacture and code. Others P chanel examples : AF 4825-AM 3423-FDS 6679-SI 4835 ETC Other example : AOD 4466 look at last number of marking code it is even (6) numbers it’s mean this is N channel mosfet and they could replace by other N channel even different manufacture and code . Others N channel mosfet examples: AO 4800 AO 4474-AP 4232-FDMC8844-SI 4812 ETC those mosfet identified only for SO8 mosfet. We can see P channel mosfet function on this “GENERAL LAPTOP MAIN POWER “ layout link : There are only 3 pcs P channel there ,2 pcs ADP(adapter) fet’s and 1pcs Bat (battery)fet .some motherboard also may have 1 adp Fet,some replace with diodes to supply every adapter supply need. I call it “VALW MAIN LINE” .from this line Battery ic and dc/dc power supply ic get VCC to powered each ic and this main VALW line also distributed adapterVoltage to every N channel Source ,before they got enable trigger to produced 3 and 5V_ALW…… P-channel mosfet works drain is a input for nagative supply and source is a output for nagative supply ,and it’s gate on with nagative volt .same way if you want to drive positive supply from p-channel mosfet then souce is input and drain is output for positive supply . This is How 2 pcs P chanel replace by 1 Dual P chanel Mosfet Look at this lay out function N channel mosfet as integrated circuit with DC/DC main power supply to produce 3V and 5V_ALW in this and what happen if P or N channel leak and what if suppose N channel replace with and P channel and what damage it could be on this How DC/DC main power supply open/close gate N channel to produce 3V and 5V_ALW and important signal enable/disable function to activate the DC/DC main supply ic (ISL 6237-RT 8206-TPS 51247) on this How do (RT8223-TPS 51125-TPS 51123)work and signal need on this If you confused ,you should read this before Introduction of System Power Laptop Motherboard in this and to avoid accident before repairing you shoul read THINGS THAT SHOULD NOT BE TAKEN IN MOTHERBOARD REPAIR We will also found (SO3) P channel ,(SO8) mean mosfet have 8pin and (SO)3 mean they have 3 pin.And this (SO3) also have P or N channel type .so be ware if you want to make replacement .just make sure replace it whit same type . Other way to Identified for (SO6) and (SO3) Mosfet transistors are by finding the marking code on ic than browse the data sheet , if they not found get mosfet location code on board than find on schema by typing marking code to adobe reader search column to look the correct marking code than browsing the datasheet again to get know mosfet type and get substitution… this is one of sample N channel (SO3) code : 2N7002 -P0603BDG samples (SO3) P channel mosfet : FDD6685 – SI12301 -TP0610K. sample datasheet link for N channel (SO3) 2N7002 :http://www.fairchildsemi.com/ds/2N/2N7000.pdf 2 mosfet in one package ,it is a simply vrm switching mosfet circuit in single mosfet package ,drain connected with diode cathode and source is connected with anode that how to identified a N-Channel mosfet. N chanel caracter common base n-channel mosfet voltage flow is drain to source for positive supply – when you apply + positive volt in gate then this mosfet drive voltage drain to souce ( gate works same as transister base) if you want to drive nagative volt from n-channel mosfet then nagative volt drive source to drain mean for nagative volt input is source and output is drain n channel mosfet logic low (vi) that mean mosfet not close circuit between the drain and source ,v_out you got vdd voltage via resistance . (Hi) when you apply vi = Hi in N-Channel mosfet ,mean drain to source connected (close circuit) in this case you got v_out source low you can got at v_out .same way in P-channel but gate work reverse as n-channel mosfet work
