Patent ID: 7443327
Filing Date: 2008-10-28
Classification: H03M

Abstract:
1. A current-output type digital-to-analog converter which receives ann-bit (n is a natural number) digital signal and outputs a constant current from a current output terminal according to the input digital signal, comprising: n output transistors each of which has a first terminal, the potential of which is fixed by a common fixed voltage and a second terminal located on a side opposite the first terminal and connected to the current output terminal; an input transistor of which has a first terminal and a control terminal commonly connected to those of the n output transistors; a first current-to-voltage conversion unit which is connected onto a second terminal side of the input transistor to convert a current flowing through the input transistor into a voltage; a constant current source which generates a reference current; a second current-to-voltage conversion unit which converts the reference current into a voltage; a first error amplifier to which, each of output voltages of the first and second current-to-voltage conversion units are input to adjust voltages at the control terminals of the input transistor and the n output transistors; n switches which are provided on a path through which an output of the first error amplifier reaches the control terminals of the n output transistors; and a control unit which controls on/off of the n switches according to the n-bit digital signal.