Low-noise, low drift, high precision linear bipolar (±10 V) voltage supply/reference for cryogenic front-end apparatus

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Abstract
A very simple linear bipolar (±10 V) voltage supply/reference (VS/R) featuring very low noise has been implemented. The noise is about 1 μVpp in a 0.1–10 Hz bandwidth, becoming, for the −10 V supply only, 1.3 μVpp at 1.5 A. The VS/R is based on commercial devices and has been designed to face the stringent requirement of very low drift systems. It features very good line regulation, less than 10 mV over 10 V at 1.5 A supply current, and very low drift, between 3 and 8 ppm/°C; it also shows large power supply rejection ratio (PSRR), >120 dB. The VS/R presented includes also safety circuits, to protect itself and the electronic equipment to be supplied in an actual experimental condition. It is protected against inversion of polarity and against under and over voltage at its inputs, and has a foldback current limiting circuit which shuts down the whole system if the current absorption lasts for some time. These protecting circuits acts on both outputs (±10 V), to maintain always the symmetry. From an analysis made on the data extracted from the measured noise spectra, it was possible to measure the dynamic output impedance, found mainly inductive, with a value of the order of 1 mH. The dc PSRR has been improved by about 20 dB with respect to the performances of the devices used, thanks to a very simple circuit solution.

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