  The complete matrix elements for $e^+e^-\to b\bar bW^\pm H^\mp$ and
$e^+e^-\to b\bar bH^+H^-$ are computed at tree-level within the Minimal
Supersymmetric Standard Model. Rates of interest to phenomenological analyses
at the Next Linear Collider are given. In particular, we analyse: (i) $t\bar t$
pair production followed by the top decays into $b\bar bW^\pm H^\mp$ and $b\bar
b H^+H^-$ final states; (ii) $H^+H^-$ signals in which $H^\pm\to h W^\pm \to
b\bar b W^\pm$ and $H^\pm\to tb\to b\bar b W^\pm$. Top and Higgs finite width
effects are included as well as all those due to the irreducible backgrounds.
