Design of a Chopper Stabilized Variable Capacitive Sense Amplifier for a MEMS Probe-Based Data Storage System

Applications of MEMS variable capacitive sensors are introduced. The design trade-offs of variable capacitive sense amplifiers are discussed and a chopper stabilized variable capacitive sense amplifier topology is introduced. The chopper stabilized topology has the advantage of not being sensitive to 1/f noise, charge injection noise, kT/C noise, and dc offsets. This circuit was designed to meet the requirements of a MEMS probe-based data storage system. These requirements include a signal-to-noise ratio of greater than 30dB and an incremental power dissipation of under 200μW per sense amplifier. The circuit was designed in HP .5 μm CMOS and laid out using NeoCell, an automated analog layout tool. The layout was extracted and the system was simulated to demonstrate linear operation and a signal-to-noise ratio exceeding 30dB.