A monolithic core for an automotive vector voltmeter

An analog integrated circuit that performs the multiplication of an input signal by a pair of sinusoidals displaced by 90° in order to provide the magnitude and phase of the input signal at an input frequency, is reported. The IC was developed to make up the core of a low-cost vector voltmeter to be used in the detection of unbalances of wheels and shafts in vehicles. A pair of Barry Gilbert´s sine shaper, operating in non-ratiometric mode, was used to produce the quadrature sinusoidals. A MOS transconductor converting the input voltage signal into a modulating term of a current that is a scale factor for the output of the sine shaper was used to accomplish the targeted multiplication. Prototypes of the circuit, implemented in BiCMOS technology have shown that the accuracy, both in phase and amplitude is better than 1%, in the range of 100 Hz to 3 kHz at ambient temperature