PURPOSE: To reduce leak of signals, form a circuit scale compact, and reduce a cost in a switch circuit.
CONSTITUTION: Using high pressure-resistant analogue switches 41'-4n' each comprising two field effect transistors 8a, 8b in inverse series connection, gate signals of the two field effect transistors 8a, 8b are controlled by optically coupled circuits 9, 10, and these are inversely biased to a source commonly connected to the field effect transistors 8a, 8b by a low impedance power supply at the time of off-action. In a switching circuit 5 for changing connection of a subject circuit, a switching diode 22 is connected to the source commonly connected to the two field effect transistors 8a, 8b of the high pressure-proof analogue switch 41'-4n', so the switching diode 22 is put on at the time of off- action of the field effect transistors 8a, 8b, thereby the low impedance power supply is connected to the source.
KANDA HIROSHI
KUBOTA JUN
