Biasoffsetdrift

Biasoffsetdrift is the gradual change in the bias and offset voltage of an electronic device, especially at the input stage of amplifiers, instrumentation amplifiers, data converters, and MEMS sensors. It manifests as a slow wander of the zero point of the output when the input is held at zero. The phenomenon is influenced by temperature, aging, supply variations, mechanical stress, and process variations in semiconductor devices. Temperature is often the dominant factor, with offset drift typically characterized by a temperature coefficient measured in microvolts per degree Celsius or parts per million per degree Celsius (ppm/°C). Long-term drift accumulates with time, contributing to accuracy loss in precision instruments.

Measurement and specification: Manufacturers specify parameters such as input offset voltage, input offset drift with temperature, and long-term offset drift. To assess biasoffsetdrift, the device is observed with a zero input while temperature is varied or with prolonged zero-input conditions to monitor drift over time.

Impact and mitigation: Biasoffsetdrift reduces DC accuracy and can masquerade as a signal in low-frequency measurements. Mitigation strategies include using devices with low offset voltage and low drift, employing chopper-stabilized or auto-zero amplifiers, differential or instrumentation configurations, careful power-supply rejection, temperature stabilization, periodic calibration, and digital compensation. Layout practices, shielding, and proper grounding also help reduce drift sources.

Applications: The concept is relevant to precision analog front ends, ADCs, op-amps, instrumentation amplifiers, and MEMS-based sensors where stable zero references are essential.