# Diference between a BJT and MOSFET

Discussion in 'Homework Help' started by AD633, Jun 23, 2013.

Jun 22, 2013
96
1
Hi,

Which of the following refers to the difference between a BJT transistor and a MOSFET

F1: The state of a BJT transistor is controlled by the voltage VCE and of a MOSFET is controlled by the gate voltage.

F2: The state of a BJT transistor is controlled by the base current of a MOSFET and is controlled by the gate voltage.

F3: The state of a BJT transistor is controlled by the collector current of a MOSFET and is controlled by the supply chain.

F4: The state of a BJT transistor is controlled by the base current of a MOSFET and is controlled by the voltage at the drain.

I think that the correct option is F2.How can i justitfy that?

I know that for a BJT the base current determines wheather the baseemitter junction is forward biased, which means that the p-doped side of the junction is at a more positive potential than the n-doped side, and the basecollector junction is reverse biased.

If the base current = 0 A then the baseemitter junction is reversly biased.

And for a MOSFET why does the Gate Voltage controls the state of operation of such transistors?

Thanks

2. ### Kermit2 AAC Fanatic!

Feb 5, 2010
3,661
887
The gate of a mosfet is widened and narrowed by the application of an electric potential. No current flows. The voltage potential creates an electric field which affects the shape of the current carrying region between source and drain.

3. ### LvW Active Member

Jun 13, 2013
674
100
I recommend to read again thoroughly F2 to F4.
How can a BJT be controlled by a MOSFET current?

Jun 22, 2013
96
1
LOL.I mistaped the sentence.It should be:

F1: The state of a BJT transistor is controlled by the voltage VCE and the state of a MOSFET is controlled by the gate voltage.

F2: The state of a BJT transistor is controlled by the base current and the state of a MOSFET and is controlled by the gate voltage.

F3: The state of a BJT transistor is controlled by the collector current and the state of a MOSFET and is controlled by the supply chain.

F4: The state of a BJT transistor is controlled by the base current and the state of a MOSFET and is controlled by the voltage at the drain.

5. ### Kermit2 AAC Fanatic!

Feb 5, 2010
3,661
887
answer 2 seems to be the correct choice of the 4 choices you gave.