An injectable depot formulation comprising crystals having structure wherein R is and the X50 value of the crystals is from 1 to 200 microns. This is accomplished with a chain of MOSFETs that are configured to operate as a chain of resistive elements or diodes wherein each element in the chain may drop a portion of a supply voltage coupled to a first end the chain. The air knife device includes at least one air knife module which receives data from the database and controls the air knife module to air blow the particular sections with contaminants. Consequently, these prodrugs may be advantageously used as therapeutic agents for IMPDH mediated processes. In this circuit configuration, even if a base current of the output-stage transistor is so determined as to permit the semiconductor device to drive the heaviest permissible load, only a reduced amount of extra current is fed to the base of the output-stage transistor when it is turned on with a light load connected to the semiconductor device.