| 摘要 |
PURPOSE: A semiconductor device is provided to automatically implement impedance matching for the external impedance. CONSTITUTION: A semiconductor device includes an output buffer connected in parallel to a plurality of transistors, a connection terminal(ZQ) connected to an external resistor and an output impedance controller(26). The output impedance controller(26) includes a first transistor(P1), a first current source, a first level controller(101) to control a gate level of the transistor, a second transistor(P2) which is connected to a source of the first transistor, a first dummy transistor group(107), a second current source, a first controllers(102,103) controlling the first dummy group. A second controllers(104,106,107,110) control transistors of output buffer. The output impedance controller(26) is connected to the connection terminal(ZQ) and the output buffer for controlling the impedance of the output buffer in response to the external resistor.
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