Linear gain control amplifier

An amplifier circuit, for use with an automatic gain control (AGC) circuit which generates an AGC signal, for in response to said AGC signal providing gain control of an input signal over a high dynamic range, said gain control being a linear function of said AGC control signal comprising:

• a compensation circuit having an input and an output, said compensation circuit capable of receiving said AGC signal at said compensation circuit input and modifying said AGC signal according to predetermined gain compensation characteristics so as to provide a modified AGC signal at said compensation circuit output;
• a first amplifier having a pair of inputs and an output, one of said first amplifier inputs coupled to said compensation circuit output and another one of said first amplifier inputs capable of receiving said input signal, said first amplifier having portions of a gain range in decibels (dB) which are piecewise linear with respect to said AGC signal, and said first amplifier gain range linear with respect to said modified AGC signal;
• a filter having an input and an output, said filter input coupled to said first amplifier output;
• and
• a second amplifier having a pair of inputs and an output, one of said second amplifier inputs coupled to said compensation circuit output and another one of said second amplifier inputs coupled to said filter output, said second amplifier having portions of a gain range in dB which are piecewise linear with respect to said AGC signal, and said second amplifier gain range linear with respect to said modified AGC signal.

An method for amplifying over a high dynamic range an input signal where signal gain in decibels (dB) is a linear function of a control signal, said method comprising the steps of:

• generating, in response to a linear control signal, a corresponding compensation signal according to predetermined gain compensation characteristics;
• amplifying an input signal at an input gain level determined by said compensation signal and providing a corresponding first amplified signal, said first amplified signal being of a gain in dB which is a linear function of said control signal;
• filtering said first amplified signal;
• and
• amplifying said filtered first amplified signal at an output gain level determined by said compensation signal and providing a corresponding second amplified signal, said second amplified signal being of a gain in dB which is a linear function of said control signal.