Offset cancellation in a transimpedance amplifier (TIA) circuit

摘要

Offset measurement and cancellation circuitry is employed in a transimpedance amplifier (TIA) circuit for directly measuring the offset in the TIA input voltage and for canceling the offset from the TIA output voltage. Employing the offset measurement and cancellation circuitry eliminates the need to use large transistors in the input stage of the TIA in order to reduce or eliminate the offset, which can increase noise and reduce Rx sensitivity. The offset measurement and cancellation circuitry of the invention obviate the need of making a tradeoff between the amount of noise and the magnitude of the offset that will be tolerated. The offset measurement and cancellation circuitry also eliminate the need for additional overhead in the decision threshold in order to avoid false triggering of the decision circuitry of the optical receiver due to noise.

主权项

1. A transimpedance amplifier (TIA) circuit configured to cancel out an offset in an output voltage of the TIA circuit caused by an offset voltage at an input terminal of a TIA of the TIA circuit, the TIA circuit comprising:
a TIA having at least a first inverting input terminal, a first non-inverting input terminal and a first output terminal, the first inverting input terminal being electrically coupled to a first optical detector, wherein an offset input voltage signal is present at the first inverting input terminal and wherein the first output terminal outputs an output voltage signal that is offset due to the offset input voltage; and offset measurement and cancellation (OMC) circuitry, the OMC being electrically coupled to the input and output terminals of the TIA for receiving the offset input voltage signal and the offset output voltage signal, wherein the OMC circuitry measures the offset input voltage signal and uses the measurement to apply an offset cancellation to the offset output voltage signal that cancels the offset from the offset output voltage signal to produce an output voltage signal of the TIA circuit that is not offset.