How to eliminate the Miller effect on BJT BC547?
Sound like you want to drive an opto-isolator with an LM231 output. 

The LM231 has an open-collector output and cannot source current- so it won't work with your circuit as shown. It doesn't have a quite enough current capability to be guaranteed to drive the 7mA you've chosen for the opto. 



Possible solutions include: 


Use a better (higher CTR) opto-isolator and drive it with 5mA. Then you need only connect the optoisolator LED to Vcc with a series resistor. 
Use a PNP emitter follower as so: 








simulate this circuit &ndash; Schematic created using CircuitLab

As I mentioned in my comments, the 4N25 with a suitable load resistor (something like 7-10K) will be very slow and may not work up to 10kHz. 



Edit: Your modified circuit will work, however use a 2N7000 or similar small MOSFET rather than an IRFB4310, use 470 ohms rather than 2K, and connect a 2K from the gate to Vcc (pullup resistor).