Patent ID: 7514980

Claim:
An exponential function generator for generating a current that is changed exponentially according to a control voltage, comprising: a voltage-current converter for converting the control voltage into a current; 1 st to n th curve generators, each for mirroring the current outputted from the voltage-current converter and to output a current corresponding to a predetermined ratio of an input current of the voltage-current converter to the current outputted from the voltage-current converter, where n is a natural number greater or equal to 2; and an output end for summing up the current outputted from each of the 1 st to n th curve generators to output a resultant current; wherein the ratios of the input current to the output current of the 1 st to n th curve generators are different from each other; and wherein each of the 1 st to n th curve generators comprises: a first current mirror for receiving the current outputted from the voltage-current converter to output a current corresponding to a predetermined ratio to the current received from the voltage-current converter; a second current mirror for receiving the current outputted from the first current mirror to output a current corresponding to a predetermined ratio to the current received from the first current mirror; and a third current mirror for receiving the current outputted from the second current mirror to output a current corresponding to a predetermined ratio to the current received from the second current mirror.