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A charge amplifier incorporates digital circuits as 1 an alternative to the classic analog amplifier to achieve a high 2 open-loop gain to maintain a consistent closed-loop gain over 3 input capacitance variations. The digital-assisted charge amplifier 4 employs a comparator, digital control logic, differential charge 5 pump, current sources, common-mode feedback, and clock gen-6 erator. A detailed analysis studies the amplifier stability and 7 trade-off between ripple voltage and settling speed. A novel two-8 step reset scheme and tri-state charge pump minimize the output 9 offset due to ripple residues. Fabricated in a 180-nm CMOS 10 process, the digital-assisted amplifier achieves an open-loop gain 11 of 101 dB, closed-loop gain of 15.0 µV/e-, input-referred noise of 12 221 erms, and output swing of 3 V while consuming 2.19 mW. 13 The amplifier also demonstrates the ability to amplify a dynamic 14 input current using a custom opto-electronic test setup. The 15 amplifier maintains a consistent closed-loop gain across parasitic 16

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