SEMICONDUCTOR DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a semiconductor device capable of automatically executing matching with an external impedance. SOLUTION: An output impedance control unit comprises: a clock generator; an up/down counter; a register; a dithering detector; a parallel-serial converter; an operational amplifier; and a transistor circuit, and includes: a first transistor connected to a connection terminal; a first constant current source for supplying a constant current to the connection terminal; a first level controller; a second transistor connected to the first transistor; a first dummy transistor group connected to the second transistor; a second constant current source; a first controller connected to the second transistor and the first dummy transistor group for controlling the first dummy transistor group so that a level at a node connected to the first dummy transistor group is equal to a preset voltage level; and a second controller for controlling transistors of an output buffer under the control of the first controller. COPYRIGHT: (C)2004,JPO