AN INEXPENSIVE PRECISION CONSTANT-CURRENT SOURCE FOR RESISTIVITY MEASUREMENTS IN HIGH TC-SUPERCONDUCTORS

The design and realization of an inexpensive, precision DC, constant c urrent source for resistance measurement of high T(c) superconductors are described. It is essentially based on easily available linear ICs and a precision voltage regulator. The circuit employs precision op.-a mps (with low drift, low noise, etc.) and is more convenient to implem ent than earlier circuits. The whole unit can be fabricated at a very low cost compared with that for commercially available units. Examples of measurements on high T(c) superconducting samples (GdBaCuO and BiP bCaSr-CuO) CuO) using this unit are also presented. The electrical cha racteristics of devices which are sensitive to intrinsic power supply transients can be determined using this current source and with suppor ting instruments.