Theoretical analysis of pulse bias heating of resistance bolometer infrared detectors and effectiveness of bias compensation

This paper analyzes the temperature rise during the pulse bias period of a resistance bolometer used for thermal radiation detection, and the effectiveness of two proposed methods for compensation of the output ramp voltage from the detector due to this temperature increase. The pulse bias heating is usually much larger than the incident radiation heating to be detected. In a focal plane array (FPA) of detectors, this heating may cause a voltage ramp equal to or larger than the fixed pattern noise (FPN) voltage caused by the pixel-to-pixel detector resistance tolerance. If no compensation is made, a large portion of the dynamic range in the succeeding redout circuitry must be reserved for this voltage ramp. This results in decreased temperature resolution of the sensor or increased complexity in the designed readout circuitry needed to meet specified performance. General expressions for the detector heating are derived to give an understanding of the important parameters. Also, two different compensation techniques are presented together with simulation results showing an effective compensation of the pulse bias heating over a 50 K ambient temperature range. An efficient compensation must consider pulse bias heating dependence on the bolometer resistance, which in turn is dependent on the chip temperature. Therefore, a sensor that operates at ambient temperature will require a compensation that considers both the chip temperature and the resistance tolerance from wafer to wafer. This is achieved by means of an on-chip sensing of the detector resistance to automatically adjust the amount of compensation.