This　study　presents　a　single-loop,　third-order,　low-power,　high-precision,　switched-capacitor　delta　sigma　modulator　(DSM)　for　a　portable　electrocardiogram　(ECG)　acquisition　device.　Several　techniques,　including　modified　feedforward　structure,　gain-enhanced　current　mirror　operational　transconductance　amplifier　(OTA),　and　dynamic　comparator,　are　adopted　to　improve　signal-to-noise　ratio　(SNR)　and　reduce　power　consumption.　Simulation　results　indicate　that　the　SNR　and　the　corresponding　effective　number　of　bits　are　100.8　dB　and　16.45　bits,　respectively,　which　fulfill　the　requirements　of　an　ECG　acquisition　system.　The　circuit　will　be　fabricated　by　the　SMIC　using　a　0.18　mu　m　general　purpose　process　in　the　near　future.