An external current injection source is provided to individual fingers of a multi-finger semiconductor device to provide the same trigger voltage across the multiple fingers. For example, the external injection current is supplied to the body of a MOSFET or the gate of a thyristor. The magnitude of the supplied current from each external current injection source is adjusted so that each finger has the same trigger voltage. The external current supply circuit may comprise diodes or an RC triggered MOSFET. The components of the external current supply circuit may be tuned to achieve a desired predetermined trigger voltage across all fingers of the multi-finger semiconductor device.