arduinoh-bridgemosfet
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.
L293D has an output current capacity of 600mA compared to L293 and SN754410 that can provide up to 1A in the outputs but apart from that the drivers have the same functionality and one can replace the other.
If you read the headlines of the SN754410 characteristics in the datasheet this is already noted
Functional Replacements for SGS L293 and SGS L293D
To turn on any of the MOSFETs properly in your circuit, the gate voltage has to be significantly higher than the source voltage. For the lower position devices Q2 and Q4, the sources are grounded to 0V therefore they can easily turn on into "saturation" by applying a gate voltage of a few volts above ground.
For the devices connected to the top rail, if you want the on-resistance between drain and source to be really low you have to obey the same rule - the drive voltage to the gate has to be several volts above the source. Now for low volt drop you want the source to be switched virtually to 6V - where in the circuit can the gate receive a voltage of maybe 9 or 10 volts?
There isn't one so please consider two options: -
Now the relays. What are you hoping to achieve here? The MOSFET whose gate is disconnected will float to some almost random voltage level and possibly turn on unexpectedly or just get hot. Get rid of the relays unless you have some cunning plan for their use which eludes me.
This is a standard H bridge using P and N MOSFETs: -
Please ask if you need recommendations for devices.
Best Answer
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.