A direct current (DC) offset canceling circuit of a trans-impedance amplifier and an automatic gain control trans-impedance amplifier is provided, including: a trans-impedance amplifier for receiving an input current and converting the input current into a first voltage signal, while the trans-impedance amplifier is provided with a plurality of inverters connected in series, wherein a sample node is defined between each inverter; a DC detector for retrieving and comparing the signals at any sample node, thereby generating a trigger signal according to the comparison; a DC eliminator for providing a path to the DC component of the input current in response to the triggering by the signal trigger, to eliminate the DC component; a reference voltage unit for outputting a reference voltage value; and a voltage output amplifier for comparing the reference voltage and the first voltage signal, to amplify the output of a second voltage signal.
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