Electronically scanned buffered direct injection circuit for staring ir

Abstract

An electronically scanned buffered direct injection (ESBDI) readout circuit is provided for a long wavelength infrared focal plane array (IR FPA). The ESBDI circuit comprises a cascoded CMOS inverter amplifier that allows high detector cell density and provides high voltage amplification, low input impedance, high charge capacity, and high sensitivity in a low power staring focal plane array. The amplifier employs a cascode FET to stabilize the amplifier operating point and to provide low noise access for each unit cell. Distributed capacitance along each bus line provides large overall charge capacity in a minimum of chip real estate. When not accessed, idle IR detector cells are clamped to an externally adjustable voltage to prevent excess detector noise and crosstalk. The circuit may be fabricated on a neutron transmutation doped silicon wafer to provide threshold uniformity and low power dissipation. For higher density applications, a common CMOS inverter amplifier may be shared among a group of detector cells within the focal plane array to reduce cell pitch and provide a high density IR FPA.