MOSFET Search - High Gate to Source Voltage

[thaitam]

Hey

I need to get a logic level mosfet which can handle in excess of 48V gate to source as a maximum.

I am not 100 % sure but If say I have a Voltage line at this 48V which goes through drain and source then I have the gate connected to a microcontroller then I will needf a very high Vgs as the microcontroller max voltage output is 3.3V.

I can only find maximum values of + or - 30V

It also obviously needs Vdss of greater than 48V

Can anybody help out? thanks

 

[ericgibbs]

Hey

I need to get a logic level mosfet which can handle in excess of 48V gate to source as a maximum.

I am not 100 % sure but If say I have a Voltage line at this 48V which goes through drain and source then I have the gate connected to a microcontroller then I will needf a very high Vgs as the microcontroller max voltage output is 3.3V.

I can only find maximum values of + or - 30V

It also obviously needs Vdss of greater than 48V

Can anybody help out? thanks

hi,
I think you are misunderstanding the Vgs, Gate to Source voltage.

If you have a N MOSFET that can be switched ON with a 3.3Vgs then the Vds voltage for the FET can be much higher, The Drain voltage will not be impressed upon the Vgs.

EXCEPT in a FET Drain to Gate failure.!! so its common practice to connect the Gate to the PIC pin via a resistor that will limit the s/c current into the PIC in order to protect the PIC.

 

[thaitam]

thanks

so say for example I have the gate voltage at 3.3V and the source voltage at 48V.

does the maximum gate to source voltage of 20 not mean that the arrangement is exceeding these maximum conditions?

 

[Hero999]

Assuming you're using an N-channels MOSFET as a high-side driver powering a 48V load, the gate voltage needs to be 51.3V relative to 0V.

The MOSFET needs to have a maximum drain to source rating of 50V (I'd say at least 60V to be on the safe side) and be able to pass the current required by the load with a gate voltage of 3.3V. If the circuit is correctly designed, the maximum gate voltage of 20V is not a problem.