Abstract: A variable frequency oscillator for an AC power supply having programmable, multiple phase outputs comprises means including a rate multiplier for generating a clock signal having a selectively controllable frequency and one or more AC signal producing stages responsive thereto. Each AC signal producing stage includes a memory storing a quarter-cycle sinusoidal waveform segment in amplitude sampled form and an address counter responsive to the clock signal for alternately addressing the memory in forward and reverse directions for producing a continuous sequence of half-cycle sinusoidal segments, an output circuit inverting every other one of the half-cycle segments.

Abstract: An auto-zeroed ohmmeter is comprised of a current source having first and second leads for connection to respective terminals of an unknown resistor to generate first and second voltages at the terminals. A sensing circuit having third and fourth leads connects to the terminals of the unknown resistor and scales the first and second voltages to third and fourth voltages respectively. A ramp generator circuit is coupled to the sensing circuit and generates a ramp voltage with a slope proportional to the difference between the fourth voltage and a multiple of the third voltage. This ramp is generated for a time period of predetermined duration to thereby produce a reference point voltage at the end of the time period.