A Preamplifier for a CdHgTe Photodetector

A preamplifier for operation with an HgCdTe-based nitrogen-cooled IR photodetector (600 nm–15 μm) is described. The preamplifier operates in the photoconductivity mode. The use of modern microcircuits made it possible to increase the bandwidth of the response to 2 MHz at a noise level of 0.5 nV/Hz1/2, which is close to the fundamental limit that is specified by the resistance of the photosensitive element. The preamplifier was used in an aperture-free scanning near-field optical microscope.