  We give a description of the continuous-variable teleportation protocol in
terms of the characteristic functions of the quantum states involved. The
Braunstein--Kimble protocol is written for an unbalanced homodyne measurement
and arbitrary input and resource states. We show that the output of the
protocol is a superposition between the input one-mode field and a classical
one induced by measurement and classical communication. We choose to describe
the input state distortion through teleportation by the average photon number
of the measurement-induced field. Only in the case of symmetric resource states
we find a relation between the optimal added noise and the minimal EPR
correlations used to define inseparability.
