This thesis presents a low-cost, high-performance, fully-integrated interface and signalconditioning ASIC (Application-Specific Integrated Circuits) for capacitive-based automotive accelerometers. The ASIC is a mixed-signal system, which comprises a switched-capacitor (SC) sense amplifier, a two-stage (SC and continuous-time) filter, a scaling output stage and a clocking module, with on-chip calibration capability. The design foundation is based on a new "injection-nulling switch" (INS). The INS has been experimentally verified to exhibit error less than 25 uV in sample-and-hold (S/H) circuit and demonstrated to be insensitive to variation of process parameters. For the ASIC design, the INS allows for simplified topology of SC front-end sense amplifier and subsequent SC building blocks without jeopardizing the performance via counteracting the impact of charge injection and clock feedthrough effects on sensitivity, resolution and offset. This has resulted in reducing power consumption of system IC significantly. The clocking module is a new programmable low-frequency clock generator based on the Miller ring oscillator that offers wide-tuning range whilst using small capacitance values, with jitter less than 300 ps at ±10% variation in 5 V supply. A new orthogonal fusible link structure design is incorporated in the calibration circuits to improve its reliability. The development of the ASIC is based on a new sensor model, which takes into account of sensor parasitic effects. The ASIC was fabricated using a standard 0.6 um CMOS technology with a die size of 2.8 mm by 2.3 mm. The accelerometer was implemented in a two-chip integrated 16-pin DIL IC, where the ASIC was bonded to a ±50 g sensing element. The IC has been experimentally tested. It has achieved a low power consumption of 10 mW (2 mA at 5 V), maximum noise root spectral density of 11.87 uV/VHz (rms noise root spectral density of 0.187 mg/VHz) at 15.63 Hz, a signal-to-noise dynamic range of 77 dB for 500 Hz bandwidth and 74 dB for 1 kHz bandwidth, and maximum clock noise of 1.562 mV.