Low-noise Amplification Readout Circuits For Highly Sensitive Detection

Low-noise readout circuits are indispensable in many detector applications.For example,output signals of detectors such as terahertz detectors and superconducting nanowire single photon detectors(SNSPD)are very low and require low-noise readout circuits to amplify the small signals.In the field of terahertz(THz)imaging applications,at room temperature NbsN6 thin film on SiO2/Si(100)substrate can achieve a fairly high temperature resistance coefficient of up to 0.5%-0.9%K-1 and an excellent THz absorption performance.In addition,with an integrated dipole antenna,at a modulation frequency of over 4 kHz,the Nb5N6 thin film on SiO2/Si(100)can achieve a responsivity of-580V/W and a noise equivalent power(NEP)of 1.7×10-11 W/? Hz,which is expected to develop terahertz array detectors with superior performance.However,in practical applications,there is no suitable low-noise readout circuit.Therefore,using a 0.18-?m CMOS process,a 1 x 16 low-noise readout integrated circuit(ROIC)is developed for a I x 64 Nb5N6 microbolometer array detector.This circuit consists of a digitally programmable current digital-to-analog converter(IDAC)and an amplifier module,which are responsible for biasing the microbolometer and amplifying its output signals with minimum added noise,respectively.The test results show that the ROIC achieves an average gain of?48 dB at 10 kl lz,a voltage-noise spectral density of?9.34 nV/? Hz,a bandwidth of 1?100kHz,and a minimum readout of 10 ? Vpp.The normalized crosstalk between channels was 0.0046.The NEP coefficient of variation(CV)between channels was only 0.059,showing good agreement.Together with the ROIC,the 1 x 64 Nb5N6 microbolomcter array detec[tor is preliminarily used for THz imaging applications.The imaging results prove that the ROIC can be used with the detector to develop an efficient and low-cost THz imaging system.SNSPD has many superior performance compared to other single photon detectors,such as-93%detection efficiency,low counts down to 10-4 s-1,near 100 MHz count rate,as low as 16 ps time jitter,and wide spectral response from visible to infrared spectrum.As for series array of superconducting nanowires,when the number of pixels in series is large,a special cryogenic RF amplifier with high input impedance will be needed to distinguish the amplitude of pulses caused by different number of incident photons.According to this requirement,a differential structure integrated low-temperature RF amplifier circuit with high input impedance was developed using IBM 0.18 ?m SiGe BiCMOS process,and its performance was characterized.At low temperature 2 K,the gain of the circuit is greater than 26 dB,with bandwidth greater than 1 GHz and low frequency cut-off frequency 0.6 MHz.The input impedance of the circuit is greater than 5 Kohms at low frequencies,and the input impedance is greater than 400 ohms at 100 MHz to meet system requirements.In the experiment of interconnecting the SNSPD with the low-temperature circuit,the results also show the excellent performance of the low-temperature circuit.The small output signal of the SNSPD can be read out with low noise,and the different amplitudes of the output pulses of the series SNSPD can be clearly distinguished.