A low cost readout and processing circuit for integrated CMOS geomagnetic sensors

This paper presents a readout and processing circuit that is integrated with CMOS geomagnetic sensor based on Hall Effect. Due to the demanding requirement in battery-powered chip, a low cost of area and power consumption design was implemented. The technique of chopper-stable structure and bipolar input transistor were adopted to reduce noise and offset. A low power dual-slope ADC follows the readout front-end and output digital output, whose integrator adopts a chopper amplifier to get improvement on precision. On chip oscillator increases the practicability of the whole circuit. The prototype circuit was produced in 0μm CMOS technology. The experimental result shows that with a supply of 3.3V, the whole power is 2.1mW and the sensitivity is 20nV/LSB.