| 摘要 |
PROBLEM TO BE SOLVED: To automatically switch capabilities of an output buffer by determining whether the capabilities of the output buffer have to be switched in accordance with the magnitude of an external load. SOLUTION: A semiconductor output circuit is provided with a reference output buffer 101 in which an output terminal external part is in a no-load state, a normal output buffer 102 which has the same capability as that of the reference output buffer 101 and in which an output terminal external part has a load, a capability variable buffer 103 which is connected parallel to the normal output buffer 102, has higher capability than the reference output buffer 101 and can control on-off, a phase difference detection circuit 104 for detecting a phase difference between an output of the reference output buffer 101 and an output of the normal output buffer 102, and a phase difference determination circuit 105 for outputting a control signal that controls the capability variable buffer 103 to turn on or off in accordance with the phase difference detected by the phase difference detection circuit 104. COPYRIGHT: (C)2004,JPO
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