| 摘要 |
PROBLEM TO BE SOLVED: To realize an output buffer which can suppress noise of a power supply attendant upon the level transition of an output signal and thereby suppress the noise of a power supply of a logic IC device, etc., mounted with a large number of output buffers to stabilize the operation and reduce the cost of a device. SOLUTION: A logic IC device, etc., mounted with many output buffers is provided with two systems of a supply voltage feeding point for outputting a high level signal with respect to an output buffer DOB and a ground potential feeding point for outputting a low level signal to the output buffer DOB. When the output buffer DOB is in state of operation and the level of its output signal DOUT is changed, output MOSFETs N2 and N3 are turned into an on-state and their substantial power supply node is connected to one system of a supply voltage feeding point VDDD and a ground potential feeding point VSSD. When the output buffer DOB is in a stationary state and the level of its output signal DOUT is not changed, output MOSFETs N5 and N6 are turned into an on state and their substantial power supply node is connected to the other system of a supply voltage feeding point VDDQ and to a ground potential feeding point VSSQ.
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