A card hopper includes a control gate that reliably allows cards of varying thicknesses to be fed individually through an outlet opening without adjustment. The hopper is configured to hold a stack of plastic cards or similar, fairly rigid, substrates. The control gate is positioned at the outlet opening and includes a flexible blade that reduces a height of the outlet opening to less than a thickness of an end card of the stack, whereby the flexible blade flexes in response to the end card when driven through the outlet opening. Also disclosed is a card feeder assembly that includes the above-described hopper.