High Gain Readout Interface Circuit for Hall Sensors for Low Power Applications

A readout interface circuit for Hall-effect sensors is provided with the capability to provide high gain while simultaneously removing offset from the sensor as well as the OpAmps. The technique used is the modified version of chopper stabilization and current spinning. Using a high pass filter as the first stage after current spinning allows the elimination of Hall offset at an early stage and hence higher amplification of the desired signal (Hall voltage). Another filtration stage after demodulation removes the offset of the OpAmps. This readout interface circuit demonstrates an improved approach to eliminate the Hall sensor offset from the output signal. It also solves the limitation of high gain that conventional readouts impose. The measured gain of the readout interface circuit is 120 V/V, providing a 3-dB bandwidth of 100 kHz.