Abstract: A precision resistor using MOS devices. The present invention utilizes an NMOS resistive element to simulate the resistor. A pair of PMOS source followers are implemented to control the value of the resistor and cancel the non-linearity due to the drain-source voltage V.sub.ds. A pair of NMOS source followers serve to eliminate non-linear distortions due to the "body effect" that can exist in the resistive element. The resistor circuit of the present invention provides higher precision, linearity and high value resistors in a smaller area than prior art MOS resistors.

Abstract: An electronic watthour meter is digitally configurable to operate as several different types of watthour meters for metering electrical energy from a variety of different electric utility services. Automatic scaling of line input currents is provided to scale the voltage input to an analog to digital converter over selected ranges such that low level and high level input signals are measured in an optimum range. A digital signal processor is employed to calculate values for metered electrical energy and output pulses, each proportional to a quantum of energy flowing in the circuit being metered. The processor calculates the value of DC offset errors inherent in the various analog circuits of the meter and uses that value in the calculation of metered electrical energy to compensate for such offset errors. The meter employs automatic and manually initiated test functions for testing the operation of the processor and other critical circuits in the meter.

Abstract: An electronic watthour meter is digitally configurable to operate as several different types of watthour meters for metering electrical energy from a variety of different electric utility services. Automatic scaling of line input currents is provided to scale the voltage input to an analog to digital converter over selected ranges such that low level and high level input signals are measured in an optimum range. A digital signal processor is employed to calculate values for metered electrical energy and output pulses, each proportional to a quantum of energy flowing in the circuit being metered. The processor calculates the value of DC offset errors inherent in the various analog circuits of the meter and uses that value in the calculation of metered electrical energy to compensate for such offset errors. The meter employs automatic and manually initiated test functions for testing the operation of the processor and other critical circuits in the meter.

Abstract: A balanced modulator for use with auto-zero networks is described. The present invention is a switched capacitor balanced modulator suitable for use in auto-zero networks where a valid input signal is available only at one phase. The present invention changes the polarity of the input signal by adjusting a switched feedback capacitor, making it possible for the switched input capacitor to sample only at one (valid) phase. The balanced modulator of the present invention may be utilized with first order auto-zero low pass filters or other switched capacitor blocks, such as gain blocks, first order high pass filters, etc.

Abstract: An electronic watthour meter for metering the consumption of electrical energy on power lines includes phase compensation means for compensating for leading and lagging phase differences between line current and voltage, whereby sampling times of the current and voltage are shifted to compensate for phase errors between the current and voltage by controlling timing signals provided to current and voltage analog to digital converters. Digital output signals from the analog to digital converters proportional to current and voltage are multiplied to provide an accurate representation of energy consumption as a result of the compensation.

Abstract: A filter for second order signals in the frequency domain. A novel switching system is described which permits a single capacitor to serve as both a termination capacitor and a sampling capacitor. A capacitor which has a value equal to the desired value of a sampling capacitor is coupled in a feedback loop of an operational amplifier. This capacitor is summed with another capacitor to result in the desired value of the termination capacitor. The present invention permits the fabrication of second order filters in a smaller silicon area than prior art methods.