Patent ID: 6556075
Filing Date: 2003-04-29
Classification: H03F

Abstract:
An amplifier system which approximates a constant output impedance during forward and reverse modes of operation, comprising:a signal amplifier which has a signal-amplifier output impedance in an enable state and transitions from said enable state to a disable state in response to a signal-amplifier disable signal DSsa; a feedback path coupled to said signal amplifier to reduce said signal-amplifier output impedance to a substantially lower enable state output impedance Zoutenbl; a reverse amplifier which has a reverse-amplifier output impedance that reduces from an off output impedance to a substantially lower on output impedance as it transitions from an off state to an on state in response to a reverse-amplifier enable signal ESra wherein said reverse amplifier is coupled to said feedback path to: a) interrupt said feedback path in said on state to thereby replace said enable state output impedance Zoutenbl with the substantially higher signal-amplifier output impedance; and b) realize a disable state output impedance Zoutdsbl that approximates said enable state output impedance Zoutenbl; and a signal generator which provides said signal-amplifier disable signal DSsa and said reverse-amplifier enable signal ESra with said reverse-amplifier enable signal ESra initiated before and terminated after said signal-amplifier disable signal DSsa.