Practical differences between Transistor and MOSFET

[amyk]

I'm trying to understand the differences between a transistor and MOSFET and why you would choose one over the other.

Since this thread title bothers me every time I read it, let me just expand it a little:

I'm trying to understand the differences between a bipolar junction transistor and a (metal-oxide-silicon) field-effect transistor and why you would choose one over the other.

A MOSFET is a transistor, just a different kind of one.

I was silently counting how many replies it'd take before someone finally spoke up. 22.

To make analogy, asking about "the difference between a transistor and a MOSFET" is like asking about the difference between food and soup. Electronics is an exacting discipline and you should learn to use the terminology carefully and precisely (even if not accurately ), as early as possible.

A guy walks into an electronics shop and asks for a transistor "to replace a broken one".
"What type of transistor? Do you know the part number?"
"It's a little black thing about this big, it's got three wires coming out of it..."
"Do you know what it says on it?"
"Dunno. It's plastic and roundish looking --- oh, like those!" (points at a tray of 78L05s)

[Ian.M]

A guy walks into an electronics shop and asks for a transistor "to replace a broken one".
"What type of transistor? Do you know the part number?"
"It's a little black thing about this big, it's got three wires coming out of it..."
"Do you know what it says on it?"
"Dunno. It's plastic and roundish looking --- oh, like those!" (points at a tray of 78L05s)

Ah, the joys of customer service in component retail   
*NOW* we know why Maplin (UK) are going out of business! 

[David Hess]

Oh no!  Not the current driven versus voltage driven BJT debate again.   As entertaining and educational as the debate can be, it's been done here before. For example this thread.

Careful study of unambiguously shows that they are voltage driven devices.  Pay special attention to the base voltage during the storage time when the base current is *negative*.  In switching circuits, we just treat them at current driven with poorly controlled current gain for simplicity and it usually works out fine.

I was silently counting how many replies it'd take before someone finally spoke up. 22.

To make analogy, asking about "the difference between a transistor and a MOSFET" is like asking about the difference between food and soup. Electronics is an exacting discipline and you should learn to use the terminology carefully and precisely (even if not accurately ), as early as possible.

I considered doing so but I would rather get on with the discussion as there was no ambiguity.  I do get annoyed when people say MOSFET transistors or JFET transistor though.  It is like saying ATM machine.

[KL27x]

Youkai, there are 100's of thousands of different transistors for sale, at this moment in time.

How do you choose? Thank god for search engines. I like to sort by price and find the cheapest one that works. 

For 5V Arduino projects, you can use either one in switching applications. In Arduino-speed switching of low voltages, FETs will generally come out on top in terms of efficiency and cost, at least if you are talking about SMD parts. There are an endless supply of great and cheap FETs which do not come in through hole packages and never will.

There is some ongoing debate regarding high voltages. But additionally frequency plays a role. In higher frequency switching, the capacitance of the gate can make FETs less efficient. Simply driving the gate can require more current than what you might be switching. But that's neither here nor there when you are working with Arduino.

I'd just go with whatever is easier for you to wrap your brain around.