This paper presents a calibration technique based on missing-code-detection (MCD) scheme to correct the gain error between the MSB and the LSB array in SAR ADCs with bridge-DAC structure. The MCD algorithm replaces the gain factor calculation with simple missing-codes count that significantly reduces the calibration digital overhead. It also relieves the linearity requirement of the testing signal; therefore, a simple charge-pump circuit can be utilized as a testing signal generator (TSG). An 80 MS/s 11-bit SAR ADC with the proposed calibration are integrated together in 65nm CMOS. It does not require any external calibration signal and the measurement results demonstrate that the calibration can improve the SNR of the ADC by 7.3 dB from 55.7 dB to 63 dB at the DC input frequency.