Patent ID: 8129977

Claim:
A variable output voltage reference voltage generator comprising: a reference voltage generating circuit that generates a predetermined second reference voltage and outputs the generated second reference voltage; and a digital to analog converter that performs digital to analog conversion for a digital signal input from outside in accordance with the second reference voltage and outputs a voltage obtained through the conversion as a first reference voltage, wherein the reference voltage generating circuit comprises: a first constant voltage circuit that operates on a power source voltage supplied from a direct current power source in order to generate a predetermined first constant voltage and outputs the generated first constant voltage, a second voltage divider circuit that divides the first constant voltage at a second dividing ratio and outputs an obtained partial voltage as a second partial voltage, an output transistor that operates on the power source voltage supplied from the direct current power source and allows a current to flow through the output transistor in accordance with a signal applied to a control electrode of the output transistor, a current-voltage converter circuit that converts the current from the output transistor into a voltage and outputs the voltage as a second reference voltage, and a second operational amplifying circuit that operates on the first constant voltage and controls the output transistor so that the second reference voltage is equal to the second partial voltage, wherein the output transistor comprises a metal oxide transistor in a source follower configuration.