Electronic switch null of horizontal S letter amendment

摘要

PURPOSE:To obtain a switching circuit without occurrence of noise and welded contact with fast response by controlling a semiconductor switching element connecting an S-shaped correction capacitor having a prescribed potential with respect to a ground level with a DC voltage from a photocoupler, and switching the S-shaped correction capacitor. CONSTITUTION:An emitter of a photodetector 56 of a photocoupler 55 connects to one terminal of a resistor 60, and the other terminal of the resistor 60 connects to other terminal of a capacitor 58. Since a potential level ea at a point A at the side of the photodetector 56 of the photocoupler 55 is selected to be H'=eb.L', FETs 51a, 51b are opened or closed by the level H' or L'. Thus, even when the S-shaped correction capacitors 44a, 44b, 49a, 49b are in any potential level such as ea, the changeover is implemented with respect to the ground level by only H or L DC voltage.