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I bought a bunch of IRFZ44Ns from China in the hopes of driving a motor bidirectionaly controls from and Arduino, but now I realise that a full bridge requires both P and N channel mosfets.. Is it possible to make a half bridge, or even a full bridge from N channel fets only?

Also, is there any reasons I don't see any schematics using IRFZ44Ns? Are they a poor choice for the application? It's only a small 4v motor.

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    \$\begingroup\$ Yes you can. The trick is to arrange for a supply about 10V (+) higher than V+, and to drive the high side FET's gates from that to turn them fully on. (+) or whatever Vgs voltage they specify Rds(on) is measured at). \$\endgroup\$
    – user16324
    Commented Jan 18, 2016 at 22:25
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    \$\begingroup\$ As an additional comment. Almost all the high current / low Rds(on) FETs offering the best performance in the market place are N-Channel parts. For this reason almost all high performance H-bridge circuits use N-FETs for both the high side and low side switches. It is also very common in these instances that boot strapping charge pump techniques are used to produce the needed higher voltage gate drive voltage for the upper FETs. \$\endgroup\$ Commented Jan 18, 2016 at 22:32
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    \$\begingroup\$ This looks like a duplicate. There are two questions which seem to already cover this: electronics.stackexchange.com/questions/208186/… and electronics.stackexchange.com/questions/79792/… Also, it is helpful to include a link to the datasheet to help people give good answers. \$\endgroup\$
    – gbulmer
    Commented Jan 18, 2016 at 22:35
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    \$\begingroup\$ @James No free lunch. [related: Question closed because yes/no answer "When asking a yes/no question there are one of two possibilities..." It may be time for you to do some research on how to drive different kinds of MOSFETs.] \$\endgroup\$ Commented Jan 18, 2016 at 22:54
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    \$\begingroup\$ Sitting in the dark brewing on what I've read I think I realise my problem anyway, because the way the n channels are referenced I need to have a gate voltage higher than that our source right? So I need to step up my gate voltage which is alot more effort than what I'm trying to avoid doing anyway.. Or something to that effect, at least. My theory of it may not be correct. \$\endgroup\$
    – James T
    Commented Jan 18, 2016 at 22:59

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Although you didnot mention the current rating of your motor and the available supply voltage I see 3 Solutions to your problem :

1-First to drive a Permenant magnet DC motor bidirectionally using an H-Bridge. you can use all N channel (this is the common practice) but you have to provide something called high side gate drive , this can be using pulse transformer , or gate driver IC , etc ... please note that even then low side mosfet need 10-15v on its gate to work properly unless it is a special type called (logic level or trech) mosfet which work at 4.5v to provide low RDS. Since your motor is 4v , i assume your battery is close to 4 maybe 6v ??

2-Another solution is to use a single mosfet in low side configuration , and use a double throw relay to reverse the motor wires . but this requires the motor to stop completey before changing direction.

3-The option most prefered for small scale applications is to buy an IC that contains the mosfets and drivers built in , inaddtion to current and thermal protection , for example : L298 L6201 DRV8816 TLE 5206 LMD18245.

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