How is a standard transistor different from a mosfet?

So I have been teaching my self the basics of electronics and I find my self confused on the differences between a standard transistor and a mosfet. 

I understand the physical differences but what I do not understand is the differences in their applications?

A transistor is either ON or OFF which is controlled from the BASE and is normally OFF.
A mosfet is either ON or OFF which is controlled from the GATE and depending on the type is normally ON or OFF.

I think I might be over complicating things but based on my description of the two above.

Am I missing anything important?


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iceng5 years ago
A mosfet is a transistor too.
Some transistors are enhanced to be on / off  devices.
Most transistors junction and mosfet have a linear response area
that is useful for analog signal amplification ( Audio too ).

Junction transistors work with a base-emitter input current controlling
a greater output collector-emitter current, while a mosfet transistor
works with a base-source input voltage controlling a large output
drain-source current.

Hope this makes it more clear for you.

A
atrumblood (author) 5 years ago
Thanks for the answers guys. I am making progress slowly.
rickharris5 years ago
A mechanical analogue to a transistor would be a valve of some kind that you can turn on and off or anywhere in between with little effort and control the flow of high pressure water through it.

A MOSFET would be more like doing the same by pinching the hose pip shut to control the flow of water.

In practical terms the MOSFET will have a much higher input impedance than the transistor. It draws very little from the input circuit. and is voltage controlled whereas the transistor is a current controlled device.
A MOSFET is STILL a transistor ! Its a transferred resistor, only the mosfet is voltage controlled and the BJT is current controlled.....
atrumblood (author)  steveastrouk5 years ago
I am not sure if that makes sense to me or not about how a BJT is current controlled and a Mosfet is voltage controlled. Aren't both voltage and current values dependent on the resistance in a circuit?

Also I should have stated in my original post that I knew both were transistors.
Basically, look at it mathematically.

Ic = Hfe x Base current for a BJT (Collector current= Hfe x Base current

But for a Mosfet.

Id= Gfs x Vg ( Drain current = transconductance x gate voltage)

Steve
NO a transistor is NOT "on or off". It is an AMPLIFIER. Without feedback, and with enough ampliification, it can give the appearance of being "on and off".
atrumblood (author)  steveastrouk5 years ago
So what is being amplified is the input or output on the base right? So a small signal on the base is mirrored in the larger input on the emitter and collector?
EXACTLY.