MONOLITHIC CRYOGENIC PREAMPLIFIERS BASED ON LARGE GATE-AREA GAAS-MESFETS

Monolithic preamplifiers using large gate-area Gallium-Arsenide Metal-Semiconductor Field-Effect Transistors (GaAs MESFETs) at the input have been designed and fabricated using an ion-implanted GaAs process. Large Sate-area is necessary to obtain low series noise. A differential voltage-sensitive preamplifier has at the input two MESFETs with a gate width W = 6000 mu m, it is fully DC coupled, has a large common-mode rejection ratio (CMRR) and dissipates low power at 4 K. Dual current-sensitive preamplifiers using at the input MESFETs with W = 24000 mu m, designed for the readout of noble liquid calorimeters, have been integrated in a single chip. Recent tests with a LAr calorimeter prototype: demonstrated strong noise reduction compared tct previous state-of-the-art hybrid readout circuits. Radiation damage tests have been performed at cold on the current-sensitive preamplifier chips.