The maximum Base current rating is 1/3rd the Collector current (1/10th in the case of Darlington transistors). In the case of 2SD2656: IC max is 1A for DC and 2A for pulse. Therefore, the max. ratings for Base current is 333mA for DC and 666mA pulse. Digital transistors are designed to ensure that the input current will be within the rated value as long as Vin is within the normal range.