Patent ID: 7615973

Claim:
An adder that converts a plurality of input voltages into currents, adds the currents obtained, converts the current added into a voltage, and outputs the voltage as an added result, comprising: a first VI converter that allows a first current corresponding to a voltage value of a first input voltage to flow; a second VI converter that allows a second current corresponding to a voltage value of a second input voltage to flow; and a current addition resistor having one end commonly connected to output terminals of the first VI converter and the second VI converter and another end grounded, which is adjustable in a resistance value, wherein each of the first VI converter and the second VI converter comprises: a prestage VI converter that generates a reference current; a poststage VI converter that generates a current corresponding to an input voltage; a first current mirror circuit having a first terminal on a reference side connected with the prestage VI converter and a first output terminal in which a current corresponding to the first terminal flows connected with the poststage VI converter; and a second current mirror circuit having a second terminal on a reference side connected with the first output terminal, which can adjust a ratio of a current that flows from a second output terminal in correspondence with a current that flows in the second terminal, and wherein the first current and the second current are allowed to flow to output a voltage generated on the one end of the current addition resistor as an addition voltage resulting from adding the first input voltage and the second input voltage together.