Patent ID: 6777959
Filing Date: 2004-08-17
Classification: G01R

Abstract:
A method of determining a resistive current of a toad comprising a load resistance and a load capacitance, the toad further comprising a capacitive current, the load driven by an input signal, the input signal being sinusoidal, the method comprising:(a) forming a first signal substantially in-phase with and proportional to the sum of the resistive current and the capacitive current; (b) forming a second signal in-phase with the input signal; (c) forming a third signal opposite in phase to the capacitive current; and (d) processing the first, second and third signals to form a first result based on the resistive current, the first result being in-phase with and proportional to the resistive current, the processing including forming an intermediate result based on the phase difference between the first result and the second signal, wherein: the first signal is based on a sense resistor in series with the input signal; the second signal is based on a resistive network coupled to the input signal and ground; and the third signal is based on a resistor-capacitor network coupled to the input signal and ground, and wherein: the resistance of the sense resistor is much less than the load resistance; the resistive network comprises a first resistor and a series-connected second resistor and the resistance sum of the first resistor and the second resistor is much greater than the load resistance; and the resistor-capacitor network comprises a third resistor and the resistance of the third resistor is much greater than the load resistance.