Methods for designing and fabricating a current mirror. A first layout is received for a first back-end-of-line (BEOL) stack that is coupled with an emitter of a bipolar junction transistor in a current mirror that has a first current ratio. A second layout for a second back-end-of-line (BEOL) stack, which differs from the first BEOL stack, is determined such that, when the second BEOL stack is coupled with the emitter of the bipolar junction transistor, the first current ratio is changed to a second current ratio. The change from the first current ratio to the second current ratio, which is based on the change from the first layout for the first BEOL stack to the second layout for the second BEOL stack, is accomplished without changing a front-end-of-line (FEOL) layout of the bipolar junction transistor.