You can use the same thing as for the MOS transistors - in this case you
have the area as parameter (or if you don't have it you can always put
several devices in parallel) is if one of the transistors has area A and the
second one has 10*A the current ratio will be 1:10. And no problems with the
Another possibility is to put resistors in the emitters. In this case the
current ratio will be mainly determined by the resistor ratio.