Patent ID: 6784720
Filing Date: 2004-08-31
Classification: H03K

Abstract:
A current switching circuit comprising:a complementary circuit connected between a first power source and a second power source having a voltage lower than that of the first power source; first and second current mirror circuits, the first current mirror circuit being connected to the complementary circuit; a first level shift element connected between the first power source and the complementary circuit, producing a voltage drop from the voltage output by the first power source to a voltage applied to the complementary circuit, through a level shift current flowing through the first level shift element; an input resistor connected between an input terminal and an input of the complementary circuit; a current path including a first transistor having a control electrode connected to the input of the complementary circuit, a first electrode coupled to the level shift element and a second electrode coupled to the second power source so that the current path extends between the first level shift element and the second power source for carrying a second current mirror current; and a second level shift element connected between the input of the complementary circuit and the second current mirror circuit, wherein in response to the input signal at a first level, the complementary circuit switches the first current mirror circuit to a first state in which the first current mirror circuit is enabled and a first current mirror current is supplied to the first current mirror circuit, and the second current mirror circuit is disabled, in response to the input signal at a second level, the complementary circuit switches the first current mirror circuit to a second state in which the first current mirror circuit is disabled, and the second current mirror circuit is enabled and the second current mirror current is supplied to the current path, and one of the first current mirror current and the second current mirror current flows through the first level shift element regardless of whether the input signal is at the first level or the second level.