Investigation Of The Influence Of Intense Magnetic Field On Electric Devices

Magnetic torquers which can produce strong magnetic field up to 0.035T at 100mm from the head are widely used for control of attitude, navigation and motion for satellites. The autocontrols of the satellite are mainly made of semiconductor devices and ususally working in the magnetic field. For that reason, it is necessary to take into consideration on the interference and destruction of the sensitive elements and important instruments in satellites.To test the influence of the magnetic field to the semiconductor devices and electric circuits, a series of experiments and theory analysis are finished. The I-V characteristic of Si and Ge diodes are measured in the constant magnetic field from 0T to 2T. The results demonstrated that on the firm voltage of the diodes, the decrease of the Ge diode reverse saturation current is more evident than that of the Si diode with the increase of magnetic field B. The reverse saturation current of Ge diode is decreased by 100nA when the magnetic field is 2T. For the forward I-V characteristics, the magnetic field has no influence on the Si diode. On the contrary, the forward current of Ge diode is reduced with the increase of the magnetic field. Other devices based on Si material, such as transistor/CMOS, are worked normal in the magnetic field. The difference of Si and Ge diodes are attributed to the carrier concentration and mobility that the former are much less than the latter.According to the theory of semiconductor and electromagnetic field, the diode I-V characteristic equation in the constant magnetic field was derived. The theory simulated plots fit the curves of the experiments very well.Some typical circuits are also work normally in the magnetic field. The main reason is that the diode/transistor/CMOS/capacity and resistor are the primary elements of the circuit. Based on conclusion above that the magnetic field has no influence on the Si devices, so there is also no influence on circuits. Magnetosensitive devices worked sensitively on the magnetic field within 0.1T.The basic devices and typical circuits can work regularly on the condition of the 0～2.5T pulse magnetic field and 0～0.35T alternating magnetic field, too.It is proved that the material with high magnetic permeability is the best candidate to shield the constant magnetic field by experiments. For example, the intensity of the magnetic field is dropped by 98 percent when it was shielded by nine-layer pure iron. This situation has reached the shielding standard for basic devices/typical circuits and Magnetosensitive device.