Cold FET Research Articles

Using cold FET to check accuracy of microwave noise parameter test set

To check the accuracy of the measurements of microwave noise parameters, verification techniques are needed. A common-gate cold FET is proposed as a noise verification standard which presents the advantage of good availability and insertability in the same test jig as employed for packaged active devices. In addition the noise parameters of a common-gate cold FET are of the same order of magnitude as the active device ones. The presented experimental data show an accuracy better than 0.1 dB on the minimum noise figure measurement.

Detection of particles by an al 20 3/ru0 2 composite bolometer

We have used a composite bolometer made of a sapphire crystal and ruthenium oxide films to detect individual particles emitted by an 241 Am source (5.5 Mev alpha and 60 Kev gamma) The experiment is done in a quick handling dilution fridge at T= 80 mK with a cold FET preamplifier. Performances of such detectors lead to consider them as realistic candidates for the detection of Dark Matter.

Broadband cryogenic preamplifiers incorporating GaAs MESFETs for use with low-temperature particle detectors

Two voltage-sensitive preamplifier designs are presented for operation at 1.6 K. Both designs incorporate GaAs MESFETs (Plessy P35-1101). The first design has two stages including a common-source gain stage and a source follower stage. The noise performance, particularly with the low-frequency noise, was found to improve with cooling. The white-noise level at low temperature is 1 nV/Hz1/2, and the low-frequency noise corner occurs at approximately 1 MHz. The voltage gain into 50 Ω is 7.0 dB, with the −3-dB point occuring at 10 MHz. The noise of the first stage was found to dominate the total noise at the output of a low-noise room-temperature post amplifier. The output impedance of the preamplifier is 50 Ω. The second design incorporates one cold FET, dissipating 1 mW, in cascode with a room-temperature bipolar transistor. The noise of this design was found to be approximately equal to that of the two-cold-stage design except for a bulge in the voltage noise centered at 13 MHz due to impedance mismatching of the line to room temperature. The gain of this design is 21 dB, with the −3-dB point at 2 MHz. Cryogenic semiconductor operation is discussed, design parameters of the two preamplifiers are discussed in detail, noise measurements are presented along with a discussion of the different temperature- and bias-dependent noise sources, and an analysis of the signal-to-noise ratio and rise time for the present detection scheme is made.