公开(公告)号：JPH11204002A

公开(公告)日：1999-07-30

申请号：JP29989098

申请日：1998-10-21

Applicant: ST MICROELECTRON INC

Inventor： GUPTA BHUSAN ,  KRAMER ALAN HENRY

IPC: H01H36/00 ,  G01B7/28 ,  H03K17/96

Abstract: PROBLEM TO BE SOLVED: To provide a switch operable by finger tips at low cost by relating the size of a signal of an output node of an amplifier to the proximity of a non-grounded object to the exposed surface, and providing a signal comparator for comparing the signal of the output node and with a reference voltage. SOLUTION: When finger tips are positioned on an outer surface 125 of a solid state switch 400, and first and second capacitors 34 and 33 are operated together with plates 23 and 24, each cycle of a circulation circuit 800 closes a switch 19 temporarily, and makes an amplifier 13 operable after an amplifier output terminal 17 is short-circuited to an amplifier input terminal 16. A signal comparator circuit 410 is provided at the switch 400, and is operated so that a signal output 17 of the amplifier 13 is compared with a grounded reference supply source a DC reference voltage 411; when the switch 400 is closed, an output lead 430 is short-circuited to the ground 432; and only when finger tips stay on the surface 125, the switch 400 is maintained in a closed state.