This disclosure describes a capacitive interface circuit for a low power
system. The capacitive interface circuit is configured to achieve very
low noise sensing of capacitance-based transducers, such as a
micro-electro-mechanical system (MEMS)-based sensor, with high resolution
and low power. The capacitive interface circuit uses a differential
amplifier and correlated triple sampling (CTS) to substantially
eliminate, or at least reduce, kT/C noise, as well as amplifier offset
and flicker (1/f) noise, from the output of the amplifier. The capacitive
interface circuit may further include an output stage that reduces
glitching, i.e., clock transients, in the output signal by allowing
transients in the amplifier output to settle. In this manner, the circuit
can be used in a low power system to produce a stable, low-noise output.