Thin film hybrid circuit resistor trimmer

Claim 1

Apparatus for trimming a thin film resistor to a desired value of resistance comprising; comparator means having two input means and an output means; standard resistance means having a value of resistance corresponding to said desired value of resistance; sense and control means having input and output means; probe means; probe excitation means having input and output terminals; said comparator means having one input means adapted to be connected across said resistor and the other input means adapted to be connected across said standard resistance means, and having its output means adapted to be connected to the input means of said sense and control means; the output means of said sense and control means being adapted to be connected to the input terminals of said probe exciting means; whereby, when a substantially null signal is detected by said sensing means, a turnoff signal is applied to said probe exciting means; one of the output terminals of said probe excitation means being adapted to be connected to said probe means, the other output terminal being adapted to be connected to said resistor; said probe means being adapted to make contact with and to be moved along the top surface of said resistor; whereby when said probe means is excited by said probe excitation means, the portion of the resistor substantially in contact with the probe means will be removed; characterized in that said probe excitation means comprises a high frequency sinusoidal power source and wherein the frequency of said power source is in excess of 20 kHz.