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 gate-area is necessary to obtain low series noise. A voltage-sensitive preamplifier with differential input, designed to operate at 4 K to readout the signal of bolometric detectors, was fabricated. Two current-sensitive preamplifiers with an input transistor of 24000 μm in gate width, 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 to previous state-of-the-art hybrid readout circuits. Radiation damage test have been performed at cold temperatures on the current-sensitive preamplifier chips