BJT vs MOSFET DC-DC SMPS Circuit

[asking]

Hello,

I have been trying to make DC-DC Buck Converter but now actually after knowing more about its complications, i would like to know how to get maximum switching frequency of any Bipolar Transistor or MOSFET ? Because in datasheet its maximum switching frequency is not written. What is Transition Frequency given in the datasheet ?

Can i use Power Transistors like TIP35C for switching DC-DC buck converter ? Because it would be easy for me to drive it using PIC Microcontroller. For MOSFET i need to use Logic Level mosfet or mosfet drivers to use with microcontroller. So Please guide me how can i know the maximum switching frequency of any BJT ? ir MOSFET ?

Thanks

 

[andreas157]

well i think that the constraint in frequency is mainly imposed by the switching losses you will have. generally switching losses, are lower in a mosfet so you can use a higher frequency. note that bjt is current controlled so it has higher losses at base.

 

[mtwieg]

MOSFETs are overall much easier to operate at high frequencies. Darlington BJTs are a very poor choice.

 

[asking]

Thanks for information

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Thanks for information