Under CopyrightHeinz, FelixFelixHeinz2022-08-252022-08-252022978-3-8396-1838-7https://publica.fraunhofer.de/handle/publica/420005https://doi.org/10.24406/publica-25310.24406/publica-253The processing of weak electromagnetic signals at radio frequencies, as needed in radio astronomical receivers or in qubit read-out, demands for low-noise amplifiers cooled to cryogenic temperatures. This work describes the characterization, modeling, and optimization of high-electron-mobility transistor amplifiers for cryogenic ultra-low-noise operation. As a result, a monolithic 4 - 8 GHz LNA with a noise temperature of 3.6 K is demonstrated.enCryogenic ElectronicsLow-Noise Amplifiers (LNAs)Small-Signal and Noise ModelingMonolithic Microwave Integrated Circuits (MMICs)TransistorsDDC::500 Naturwissenschaften und Mathematik::530 Physik::537 Elektrizität, ElektronikDDC::600 Technik, Medizin, angewandte Wissenschaften::620 Ingenieurwissenschaften::621 Angewandte Physikdoctoral thesis