A novel design of an open loop micromachined accelerometer is presented. The mechanical structure of the accelerometer is fabricated using bulk micromachining, which is then attached to a CMOS chip containing photodiodes and their readout electronics. The photodiodes are used to sense the movements of the proof-mass due to acceleration. Modeling of the accelerometer including the mechanical, electrical and optical behavior of the sensor as well as analysis of all its noise sources is described. A general expression for the noise equivalent acceleration (NEA) of the sensor is derived. A cantilever suspended accelerometer is presented as a case study, its NEA is derived and its optimal design with respect to the NEA is discussed. Finally, the fabrication and characterization of a first prototype are presented. The prototype shows a NEA of about 85 μg/ √Hz, a natural frequency of about 1.2 kHz and a maximum acceleration > 5 g.