While scrolling through an online document, I came across the statement, "If charges carried by the black hole are large, the curvature at the horizon is small." How is this so? 

I tried to think of an answer to this. My thinking goes this way: I know curvature is related to mass. If an object is more massive, it bends the spacetime fabric more, producing large curvature. So curvature small means mass small. So how does a large charge mean a small mass for a black hole? What is the relationship between the charge and mass of a black hole?