Conversion of MOSFET to BJT

[girish1989]

Hi All,

Is there any possiblity to convert a Mosfet to Bjt. Please do let me know if there is any way to do the same.
Please do help me in converting a MOSFET to BJT.
Do the needful





Thanks,
Girish S

 

[LvW]

Hi All,

Is there any possiblity to convert a Mosfet to Bjt. Please do let me know if there is any way to do the same.
Please do help me in converting a MOSFET to BJT.
Do the needful
Thanks,
Girish S

A MOSFET is a MOSFET and a BJT is a BJT.
Both have different properties - and I see no reason and no possibility to "convert" one to each other.
Another task could be to modify a certain circuit - for example: an amplifier stage - by replacing a MOSFET by a BJT without changing the gain value.
But this has nothing to with a "MOSFET-BJT conversion".

 

[girish1989]

A MOSFET is a MOSFET and a BJT is a BJT.
Both have different properties - and I see no reason and no possibility to "convert" one to each other.
Another task could be to modify a certain circuit - for example: an amplifier stage - by replacing a MOSFET by a BJT without changing the gain value.
But this has nothing to with a "MOSFET-BJT conversion".

Y not??
A mosfet needs certain voltage to operate and a BJT needs a certain current to operate.
A small modification in MOSFET transistor can make that work. Coz, I have seen a zener diode at the gate and source of a mosfet to operate as a BJT.
But I dint understand that.
I might be wrong also but if I am correct I can learn something out of it.

 

[KerimF]

As you said, the base of the BJT needs, practically speaking, current not voltage.
But for the conversion to be properly done, the original MOSFET circuit and its load should be specified first.

 

[LvW]

Coz, I have seen a zener diode at the gate and source of a mosfet to operate as a BJT.
But I dint understand that.

If you have seen such a way to convert a MOSFET into a BJT - show us the corresponding parts and we can try to explain.

- - - Updated - - -

As you said, the base of the BJT needs, practically speaking, current not voltage.

Current - not voltage? Are you sure? What about Shockley`s equation (exponential relationship between Vbe and Ic)?

 

[kripacharya]

Just connect a resistor between Gate & Source, and Mosfet will behave like Bjt for your purposes

 

[KerimF]

You are right LvW about the "exponential relationship between Vbe and Ic"... this is why I added the expression... "practically speaking"

 

[LvW]

You are right LvW about the "exponential relationship between Vbe and Ic"... this is why I added the expression... "practically speaking"

OK - that makes sense. In short: The BJT is a voltage-controlled device - however, a base current cannot be avoided and is "practically" a fixed percentage of the collector current.

- - - Updated - - -

Just connect a resistor between Gate & Source, and Mosfet will behave like Bjt for your purposes

That`s all? What is the value of this resistor?
What about the exponential relationship between input voltage and output current?

 

[ArNvC]

Ib comes from Ic by forward biasing the BE junction...Ic=beta*Ib is what is taught but people don't decipher the truth.

Just connect a resistor between Gate & Source, and Mosfet will behave like Bjt for your purposes

dosen't make any sense...how?