I have a four phase square wave current source which I will drive inductors. As a matter of fact I need to increase my 1.2 mA peak current to 420 mA peak. Is there any simple method by using power transistors or any transistor for this purpose?

Thanks.

 

Do you have a circuit for the current source?

 

Look up emitter follower, compound emitter follower, source follower.

They are relatively simple to implement.