SEMICONDUCTOR DEVICE

摘要

PURPOSE: A semiconductor device is provided to automatically perform the impedance matching to the external impedance. CONSTITUTION: A semiconductor device includes an output buffer, a connection terminal and an output impedance controller(26). A plurality of transistors are connected to the output buffer in parallel. The connection terminal is connected to the external resistor. The output impedance controller(26) includes a first transistor, a level controller, a first dummy transistor array, a first controller and a second controller. The output impedance controller(26) is connected to the connection terminal and the output buffer. The output impedance controller(26) controls the impedance of the output buffer in response to the external resistor. The level controller is connected to the gate of the first transistor and controls the level of the gate of the first transistor to set the connection terminal to a previously set voltage level. And, the second controller controls the transistor of the output buffer in response to the control performed by the first controller.