A 24-bit multi-functional sensor analog front end employing low noise biasing technique with 8.2nV/√Hz input referred noise

An Analog Front End (AFE) for a multi-functional environmental sensor is proposed. The IC consists of a 8.2nV/VHz input referred noise, 0.22mm area instrumentation amplifier, a 25aC/√Hz, 0.12mm2 charge amplifier, and a 24bit continuous-time delta-sigma ADC, which are designed with a weak inversion biasing technique. The AFE has been fabricated in a 0.18μm CMOS process with 4.5mm2 die area. The current consumption at 2.56kHz output data rate is 2.5mA, reducing to 2μA at 0.01Hz.