I am working on a project of multiple output SMPS.
I am working on 100 kHz frequency and I need a driver circuit for it. I am using 6N137 optocoupler. I was previously using TPN2222A amplifier in cascade with 6N137, but it is not working on more than 10 kHz.

can anyone tell me the amplifier transistor which can be added in cascade with 6N137 to make driver circuit for 100 kHz frequency mosfet.

I am posting the circuit diagram of driver circuit used for 10 kHz.

 

The 6N137 data sheet shows a 350 ohm collector resistor to obtain high frequency performance. The 4.7k ohm resistor you have is too high. Try using a value below 1k ohm.

You will also likely need a push-pull or totem-pole type driver for the MOSFET since they have high gate capacitance that must be rapidly charged a discharged. You might consider a MOSFET IC driver made for that purpose. There are many available.

 

You might also consider using digital isolators instead of optocouplers.

Have a read through this article:
http://www.eetimes.com/design/power...synchronous-rectifiers-with-digital-isolators