Abstract: A method and apparatus is provided for varying the characteristics of an output signal of a current generator based on the impedance of a load to which the output signal is applied. The current generator contains first and second voltage inputs and outputs the output signal based on a voltage difference applied across the first and second voltage inputs. The first voltage input receives an externally applied input voltage, and the second voltage input receives the output of a comparator which has a negative input for inputting the external input voltage and a positive input for inputting the output voltage of the current generator. Based on the above configuration, if the load of the impedance is relatively small, the voltage of the output signal is less than the externally applied input voltage, and the comparator outputs zero volts to the second voltage input. Thus, the current value of the signal output by the current generator is dependent upon the external input voltage.