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In this paper, we discuss a few techniques that allow an effective reduction of the background noise and/or the reduction of the measurement time when performing voltage noise measurements by employing a number of nominally identical voltage amplifiers with negligible equivalent input current noise. It is demonstrated in particular that, if $N\ (N > 2)$ voltage amplifiers are connected to the device under test and if the properties of cross-correlation among all $N$ acquisition channels connected to the output of each amplifier are exploited, the time required for obtaining a given accuracy is reduced by a factor $N(N - 1)/2$ with respect to the conventional setup for cross-correlation that employs only two channels. From another point of view, the effective background noise is reduced for constant measurement time. Such a factor can be further increased if amplifier paralleling is also employed for reducing the equivalent input voltage noise for each channel. Measurements on two different setups employing up to four channels and up to eight channels are presented that confirm the expected reduction factors in measurement times.

In this paper, the authors demonstrate that a proper connection of two or more low-cost low-accuracy digital-analog converters can be used for the realization of a high-accuracy static analog memory (SAM). High-accuracy SAM is a circuit behaving as a high-accuracy sample and hold block with indefinite hold capability. The proposed topology can be applied both at the board level and at the integrated-circuit level when designing compact and low-cost devices for automated test equipment. In fact, as it will be demonstrated in this paper, high accuracy can be guaranteed by design, without the need for any calibration procedure. The proposed approach can therefore be considered as a possible and advantageous alternative to the conventional methods employed for the realization of high-accuracy multiple-output programmable voltage or current sources. A prototype of the SAM, based on the proposed approach, has been assembled and tested. As it will be shown, the obtained experimental results fully confirm the validity of the approach

Ultralow noise measurements often require the application of signal processing and correction techniques to go beyond the noise performances of front-end amplifiers. In this paper, a new method for the voltage noise measurement is proposed, which allows, at least in principle, the complete elimination of the noise introduced by the amplifiers used for the measurements. This is obtained by resorting to the conventional cross-correlation technique for the elimination of the contribution of the equivalent input voltage noise of the amplifiers and by using a new three-step-measurement procedure that exploits different amplifier-configuration measurements in order to subtract the contribution of the equivalent input current noise of the amplifiers