| 摘要 |
<p>PURPOSE:To obtain a 'Normally-on-type' relay that holds an ON state when no input signal is present and set itself in an OFF state only when an input signal is present, by using a depletion type, field effect transistor as an output element for a relay. CONSTITUTION:The control as a relay is established by a method wherein the electric signal from an input terminals 7 and 8 is converted into a light- signal in a light-emitting element 1, the light-signal is converted into an electric signal again in a photo-receiving element 2 and fed into the gate of a FET3 to perform the ON/OFF changeover. In this case, a depletion type element is used for the FET3 as the output element, and the terminal of the photo- receiving element 2 is connected to the gate and the source of the FET3 in the direction where the voltage VGS between the gate ad the source will be VGS<VTH<0 with respect to its threshold voltage VTH in the case of N-type and will be VGS>VTH>0 in the case of P-type. With those relations met, it is possible to obtain a 'Normally-ON-type' relay that cuts off itself by turning off the FET3 only when a signal is fed and hold its conduction state when no signal is present.</p> |
