DC and offset cancellation for fully differential optical receiver

A method comprising:

• converting, using a transimpedance amplifier, differential current signals to differential intermediate voltage signals;
• amplifying, using a main amplifier, the differential intermediate voltage signals to generate differential output voltage signals;
• cancelling a DC component of the differential output voltage signals using a fully-differential DC cancellation circuit;
• regulating, fully differentially, common-mode voltage between an input of the transimpedance amplifier and an output of the transimpedance amplifier;
• and
• detecting common mode voltage at both an input and an output of the transimpedance amplifier using a voltage divider spanning outputs of the transimpedance amplifier.

An apparatus comprising:

• a pair of photodetectors;
• a transimpedance amplifier in communication with the photodetectors;
• a main amplifier in communication with the transimpedance amplifier;
• a fully-differential DC cancellation circuit in communication with an output of the main amplifier, the fully-differential DC cancellation circuit configured to cancel a DC component of the output of the main amplifier by processing signals from an input and an output of the transimpedance amplifier and from an output of the main amplifier;
• and
• a residual offset-voltage adjustment circuit comprising a pair of differential transistors that controls a voltage offset of the output of the main amplifier.