Abstract: Gas generating apparatus in which a supply of carrier gas is mixed with an impurity gas that permeates through the membrane of an impurity gas generator. A dopant gas is supplied to the impurity gas generator through a pressure controller which operates in response to a pressure monitor that monitors the pressure of the dopant gas supplied to the impurity gas generator. As the monitored pressure of the supplied dopant gas changes, the pressure of that supplied gas likewise changes in a manner which maintains a substantially constant flow rate of the impurity gas through the membrane to be mixed with a carrier gas.

Abstract: A device adapted to generate a gas flow containing a precise amount of impurities. The device comprises a membrane through which an impurity gas peremeates and mixing means to make a mixture of said impurity gas and a vector gas sweeping said membrane. The pressure of said mixture is substantially constant, but adjustable, to enhance the accuracy of the device.