A new type of active device composed of metals is fabricated based on
the galvanomagnetic electromotive force effect, which is at the origin
of the magnetoresistance effect and of the so-called planar Hall effe
ct. A power gain (the ratio of the signal output to a signal input) of
2.5 is experimentally obtained for this active device. This experimen
tal result shows the feasibility of active devices based on quite a di
fferent principle from existing ones. (C) 1997 American Institute of P
hysics.