Fully-faithful functors between categories of modules

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Let $f\colon A\to B$ be an injective homomorphism of associative rings. It induces the faithful functor $F\colon B\text{-mod} \to A\text{-mod}.$ Are there any known conditions on $f$ for $F$ to be full (i.e. the $B$-mod is a full subcategory of $A$-mod)?