A Time Domain Multiplexer for Large Arrays of High Impedance Low Temperature Bolometers

We present a time domain multiplexer for high impedance bolometer arrays. It is based on the use of quantum-point-contact high-electron-mobility-transistors (QPC-HEMTs) as low temperature switches and a cold FET amplifier with programmable auto-zero-circuit. We employ the high bolometer resistance (about 10 MΩ) in parallel with a capacitance as antialiasing filter. A new generation of QPC-HEMT reaches a noise level close to the expected one. We will use this approach to multiplex the pixels of a mm-wave bolometric camera destined for the 30 meter IRAM telescope at Pico Veleta.