A 0.32 $\times$ 0.12 mm $^{2}$ Cryogenic BiCMOS 0.1–8.8 GHz Low Noise Amplifier Achieving 4 K Noise Temperature for SNWD Readout

A significant number of cryogenic low-noise amplifiers (cryo-LNAs) are required for the readout of superconducting nanowire detector (SNWD) arrays. It is desirable to have compact cryo-LNAs in place so that the size of the readout circuitry for the SNWD array can be reduced. In this study, we first examined the bandwidth, linearity, and noise requirements of the cryo-LNA for SNWD readout. After that, the design and implementation of a wideband silicon–germanium (SiGe) BiCMOS cryo-LNA were described in detail. The LNA features two cascode stages with resistive shunt–shunt feedback for wideband input impedance matching. The capacitive peaking techniques and emitter inductive degeneration via a slab inductor were utilized to increase the bandwidth without compromising the layout’s compactness. To ensure the amplifier works well at cryogenic temperatures, we modified the model parameters from the foundry-provided models based on the device’s reported cryogenic test data. The measurement results at 3.6 K demonstrate that the cryo-LNA, occupying a core size of only 0.03 mm $^{2}$ , achieves a noise-equivalent temperature (NET) of 4–10 K and an average gain of 30.5 dB in the frequency band from 0.1 to 8.8 GHz, under a power consumption of 8.2 mW. We successfully integrated this LNA with a quantum sensor array on a printed circuit board (PCB) and obtained favorable test results, demonstrating the potential application of LNAs for reading large-scale SNWDs.