Feed-forward biasing for RF amplifiers

An integrated circuit device adapted to provide bias currents to one or more radio frequency power amplifiers in an amplification signal path, said integrated circuit device comprising:

• an input for receiving a radio frequency signal to be amplified by the one or more radio frequency power amplifiers;
• a level sensing circuit coupled to said input and adapted to provide a bias control signal proportional to a relative magnitude of the radio frequency signal to be amplified;
• and
• a biasing circuit coupled to said level sensing circuit and adapted to output bias currents to the one or more radio frequency power amplifiers, each said bias current proportional to said bias control signal, and said biasing circuit configured to scale said bias currents such that each successive radio frequency power amplifier in the amplification signal path receives a proportionately larger bias current.

A biasing circuit for use with a radio frequency power amplifier, said biasing circuit comprising:

• an input for receiving a radio frequency signal to be amplified by the radio frequency power amplifier;
• level sensing circuitry comprising a filter circuit coupled to said input and a first transistor circuit coupled to said filter circuit and adapted to provide a bias control signal having a value proportional to a relative magnitude of the radio frequency signal to be amplified;
• and
• biasing circuitry comprising a second transistor circuit coupled to said first transistor circuit and adapted to output a bias current to the radio frequency power amplifier that is proportional to said bias control signal;
• wherein said level sensing circuitry substantially rectifies a radio frequency signal to be amplified by the radio frequency power amplifier to generate a substantially DC bias control signal that is proportional to a relative magnitude of the radio frequency signal to be amplified, such that said bias current output by said biasing circuitry is a DC bias current signal having a magnitude proportional to the relative magnitude of the radio frequency signal to be amplified.

A biasing circuit for use with multiple radio frequency power amplifier stages successively arranged in an amplification signal path, said biasing circuit comprising:

• an input for receiving a portion of a radio frequency signal to be amplified by the multiple radio frequency power amplifiers in the amplification signal path;
• a filter circuit coupled to said input and adapted to pass a desired range of signal frequencies within the radio frequency signal to be amplified;
• a first transistor circuit coupled to said filter circuit and adapted to output a bias control current based on receiving a filtered portion of the radio frequency signal to be amplified through said filter circuit;
• and
• a biasing transistor network coupled to said first transistor circuit and adapted to output multiple bias currents for biasing the multiple radio frequency power amplifiers based on mirroring said bias control current with a different current gain for each one of said multiple bias currents;
• wherein the current gain for a given one of said multiple bias currents is configured based on a maximum signal amplitude expected for a corresponding one of the multiple radio frequency power amplifier stages, such that each successive radio frequency power amplifier stage receives a proportionately larger bias current from said biasing circuit.

A method of biasing a first radio frequency power amplifier, said method comprising:

• sensing a relative magnitude of a radio frequency signal to be amplified by the first radio frequency power amplifier;
• generating a control current proportional to the relative magnitude of the radio frequency signal to be amplified;
• mirroring the control current with a first desired current gain to produce a bias current proportional to said control current;
• wherein said bias current is configured with the desired current gain based on a maximum expected signal amplitude of the radio frequency signal to be amplified, and wherein said bias current varies with the relative magnitude of the radio frequency signal to be amplified such that the first radio frequency power amplifier operates in a substantially linear mode across a range of relative magnitudes of the radio frequency signal to be amplified.