  We analyze the effect of the quantum noise of an amplifier on the
entanglement properties of an input state. We consider both phase insensitive
and phase sensitive amplification and specialize to Gaussian states for which
entanglement measures are well developed. In the case of phase insensitive
amplification in which both the modes are symmetrically amplified, we find that
the entanglement in the output state vanishes if the intensity gain exceeds a
limiting value $2/(1+\exp[-E_N])$ where $E_N$ is the logarithmic negativity of
the input state which quantifies the initial entanglement between the two
modes. The entanglement between the two modes at the output is found to be more
robust if only one mode is amplified.
