Voltage proportional replication device using magnetoresistive sensing elements

A voltage proportional replicating device comprising an input electromagnet responsive to an input voltage for producing a magnetic field in proportion to said input voltage;

• a first magnetoresistive sensing element disposed within the field of said input electromagnet;
• an adjustable source of output voltage;
• an output electromagnet responsive to said output voltage for producing a magnetic field in proportion to said output voltage;
• a second magnetoresistive sensing element disposed within the field of said output electromagnet, at least one of said first and second magnetoresistive sensing elements comprising a compound of the form A.sub.w B.sub.x C.sub.y O.sub.z where A comprises one or more rare earth elements, B comprises one or more elements chosen from the group consisting of Mg, Ca, Sr, Ba, Pb and Cd and C is one or more elements from the group consisting of Cr, Mn, Fe and Co, said at least one sensing elements responsive to ac voltages over the range 10.sup.3 to 10.sup.8 Hz;
• and
• a control circuit for controlling said adjustable output voltage to maintain a constant ratio between the resistances of said first and second magnetoresistive elements, thereby maintaining a constant ratio between said input voltage and said output voltage.