Design Of Array Nb₅N₆ Microbolometer Readout Circuit

High-sensitive terahertz detector is the key of the development of terahertz technology. Nb5N6 micorbolemeter THz detector is a kind of microbolometer fabricated of Nb5N6 thin film. It has the advantages of working in room temperature, high sensitivity and fast response time. At the same time, the fabrication is so easy that it’s suit for large array integration. In this thesis, the structure, operational principle and characteristic parameter of the Nb5N6 microbolometer are researched. Based on the low noise, high impedance and high response rate of the Nb5N6 micorbolemeter, a high-input-impedance low-noise readout circuit for 1×64 array Nb5N6 microbolometer is designed.For the requirement of Nb5N6 microbolometer’s miniaturization use, the readout circuit, which is modelar designed, contains of the following several functional modules. The DC bias module supplies adjustable current range from 0 to 0.5 mA for 64 Nb5N6 microbolometers. The signal amplification module made by low noise operational amplifier LT1028 amplifies the weak signal through the impedance conversion and negative feedback system. The multichannel gating module consisting of digital circuit and analog circuit converses the parallel signal to serial signal by multi-channel switch ADG732, then amplifies it. The data collecting module realised by Embedded SCM Arduino DUE R3 samples the signal and implements the analog-to-digital conversion as well as storage.The parameters of the 64-channel low-noise readout circuit are as follows:the single channel input impedance is as high as 100 kΩ, the bandwidth is 35 kHz in which the gain is up to 59 dB. The equivalent noise of the circuit as low as Nb5N6 microbolometers’is 6.4 nV/Hz1/2 at 1 kHz. The gain and noise of the circuit between the 64 channels have high consistency, and the variance of each channel’s gain is 8.6%.We combine NbsN6 microbolometers array with the circuit and test them by an optical measurement system. Direct scanning detection of terahertz signal of 280 GHz and 650 GHz is successfully realised.