Google for 'difference between BJT and MOSFET' for more information. P-channel MOSFETs are not preferred (over N-channel) but using an N-channel device in the upper position requires a gate voltage some volts higher than the upper rail voltage. The BJT will have a VceSat of at least 0.2V, perhaps much more at high current, so is not the preferred switching device for high current. They are preferred for switching heavier currents. The MOSFET will drop less voltage thus generating less heat. ![]() The big difference is in VceSat (of the BJT) and RdsOn of the MOSFET. There are logic level devices that reduce this Vgs but never to just 0.7V. In both cases, for the MOSFET, the Vgs (Voltage gate to source) often needs to be several volts. For the upper device, the same thing happens in reverse, the base needs to be 0.7V lower than the emitter tied to the upper rail. ![]() The transistors are easier to turn on for the bottom device, the base needs to be 0.7V higher than the grounded emitter. Same for the upper device: I can use a P-channel MOSFET or a PNP transtor. I can use an N-channel MOSFET at the bottom of an H-Bridge and I can use an NPN transistor just as well. Is that correct? What if the thing I'm trying to control is a 6v DC motor that I'm happy to have run at the same 5v the Arduino runs at? In that case is there a difference between MOSFET and transistor? Will one heat up faster than the other?Īctually, none of those ideas are quite correct. Where as with an Arduino-transistor setup you are limited to an equipment with a maximum of 5v since that's what the Arduino/Transistor are running at. This would mean that with something like an Arduino you could use a MOSFET to control an arbitrarily large piece of equipment requiring practically any voltage needs. Please correct me if I'm wrong but my understanding of the "for dummies" difference between MOSFET and a transistor is this: Transistor - all 3 pins on the same voltage MOSFET - switch pin is very low voltage, circuit pins can be significantly higher voltage up to whatever the MOSFET is rated for. I'm trying to understand the differences between a transistor and MOSFET and why you would choose one over the other. In another thread someones suggested to me using an H-bridge/MOSFET setup to control a DC motor.
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