Open loop variable gain amplifier using replica gain cell and signal amplification method

A variable gain amplifier ('VGA') having an open loop architecture is disclosed. The VGA includes one or more gain cells coupled in the signal path to amplify a given input signal. The VGA further includes a replica gain cell having a gain servo circuit which amplifies a gain reference signal according to a programmable gain input and equalizes the amplified reference signal to the original unamplified reference signal, continuously generating a gain control input to the signal path gain cells based on the equalization. This gain control input reflects the gain set by the programmable gain input as adjusted for process, temperature and supply voltage variations. The replica gain cell further includes a common mode voltage servo circuit which senses the common mode voltage of the amplifiedreference signal and equalizes it to a common mode voltage reference, generating a common mode voltage control signal to the signal path gain cells to regulate their common mode voltage. This regulation of the common mode voltage of the signal path gain cells is compensated for process, temperature and supply voltage variations.