PAD capacitance nulling circuit for QWIP-ROIC hybridisation

A PAD capacitance nulling circuit has been investigated to be used in quantum-well infrared photodetector to read-out integrated circuit (QWIP-ROIC) hybridisation. Simulation results show that it is possible to cancel the parasitic capacitance of an analogical PAD in the specific range of detection of a QWIP (outputs from 0.2 to 13 nA). For the same QWIP-ROIC interface, the voltage was found to vary approximately 0.24 mV (0.008 ) as opposed to 120 mV when the circuit is not used. Even though the presented circuit has been designed for this specific application, it shows great potential to be employed in all circuits where the input signal is a current and parasitic capacitances in the path of the signal are undesired.