High output impedance current source

A current source comprising:

• a voltage-to-current converter having an input for receiving a voltage waveform and an output for outputting a current waveform to a load at an output impedance for the voltage-to-current converter, the voltage-to-current converter including resistance control means for adjusting the output resistance of the voltage-to-current converter under computer control, an output resistance being high with respect to the magnitude of an impedance of the load and the output impedance having a non-zero output and stray capacitance;
• and
• an inductance synthesis circuit operatively connected to the output of the voltage-to-current converter for synthesizing a selected inductance, the inductance synthesis circuit including inductance control means for adjusting and controlling the value of the selected inductance to a level to cancel the contribution of the output and stray capacitance to the output impedance of the voltage-to-current converter at a selected operating frequency, the inductance synthesis circuit causing application of the selected inductance to the output of the voltage-to-current converter so that an overall output impedance of the current source at the load is high and controllable.