Representations of twisted tensor products

We obtain a faithful representation of the twisted tensor product $B\otimes_{\chi} A$ of unital associative algebras, when $B$ is finite dimensional. This generalizes the representations of [C] where $B=K[X]/<X^2-X>$, [GGV] where $B=K[X]/<X^n>$ and [JLNS] where $B=K^n$. Furthermore, we establish conditions to extend twisted tensor products $B\otimes_{\chi} A$ and $C\otimes_{\psi} A$ to a twisted tensor product $(B\times C) \otimes_{\varphi} A$.