CMOS amplifier providing automatic offset cancellation

A post-amplifier circuit for use in a fiber optic receiver, said post-amplifier circuit being responsive to a substantially DC balanced input data signal, and operative to generate an amplified data signal, the amplifier circuit comprising:

• a limiting amplifier responsive to the input data signal and to an error correcting signal, and being operative to generate the amplified data signal, said limiting amplifier including,
• a first amplifying stage having an input port for receiving the input data signal, and an output port for receiving the error correcting signal, said first amplifying stage being responsive to said input data signal and to said error correcting signal, and operative to generate a first stage amplified signal at said output port,
• a second amplifying stage responsive to said first stage amplified signal, and being operative to provide a second stage amplified signal, and
• a third amplifying stage responsive to said second stage amplified signal, and operative to generate the amplified data signal, each of said first, second, and third amplified stages being implemented using complementary metal oxide semiconductor (CMOS) technology in accordance with source couple logic;
• and
• a feed back circuit responsive to said second stage amplified signal, said feed back circuit being operative to generate said error correcting signal, said feed back circuit including,
• a low pass filter responsive to said second stage amplified signal, and operative to generate a filtered signal, and
• an error amplifier responsive to said filtered signal, and operative to provide said error correcting signal to said limiting amplifier;
• whereby offset voltage caused by process characteristics of said limiting amplifier and temperature variations in said limiting amplifier are canceled by said feedback signal.