High Input Impedance Cryogenic RF Amplifier for Series Nanowire Detector

We designed a high input impedance cryogenic radio frequency amplifier to scale up a series array of superconducting nanowire single photon detectors for resolving a wide range of photon numbers. The monolithic integrated chip was fabricated by Tower Jazz's 0.18-μm SiGe BiCMOS process. Temperature dependence of the main components, such as silicon germanium heterojunction bipolar transistor, proportional current source, and poly resistor, were characterized to estimate the quiescent point of the amplifier at cryogenic environment. At 4.2 K, a cryogenic amplifier with 6-kΩ input impedance, 20-dB gain, 4 MHz to 1-GHz bandwidth, and 0.9-mW power dissipation was obtained.