Cryogenic Concept of a Low-Noise Amplifier Using IHP 130-nm BiCMOS Technology

Cryogenic low-noise amplifiers (LNAs) are critical components for the readout of cryogenic sensors. Placing readout circuitry in close proximity to the detector at cryogenic temperatures minimizes the length of interconnections prior to the first amplification stage. Low-temperature operation can also significantly enhance LNA performance. However, microelectronics foundries do not typically provide device models for cryogenic operation. Therefore, characterization and validation of the technology at these temperatures are required before designing a full integrated circuit. This paper proposes a conceptual design for a cryogenic LNA optimized for the readout of a Superconducting Quantum Interference Device (SQUID). To manage power dissipation at cryogenic temperatures, the LNA is also designed for operation at intermediate temperatures. Consequently, the target operating temperature range is from 77K to 300K. The design focuses on a fully differential voltage amplifier to achieve high common-mode noise rejection. The LNA's first stage is based on a differential pair of SiGe heterojunction bipolar transistors (HBTs), selected for their low-noise and high-speed characteristics. Operating HBTs at cryogenic temperatures enhances both transconductance and current gain. The design is implemented in IHP's 130nm SiGe BiCMOS technology. Key cryogenic measurements, including current gain (β) and transconductance efficiency (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g_m/I_c</i>), are presented and discussed.