CMOS analog sine function generator using lateral-PNP bipolar transistors

Abstract

An implementation in CMOS technology of the ingenious analog sine function generator invented by Barrie Gilbert over two decades ago (Electron. Lett., vol. 13, pp. 506-508, 1977) is described in this paper. New in this circuit is the use of lateral-PNP bipolar transistors to build the core of the sine generator together with MOS transistors in the saturation region making up the rest of the circuit. Experimental results from prototypes of the circuit fabricated in 0.8 /spl mu/m CMOS technology showed that the accuracy of the produced sine is lower than that reported from implementations in bipolar and BiCMOS technologies (dos Reis Filho and Fruett, Proc. ICECS'97, 1997). The measured deviation from ideal sine over the (-/spl pi//2 to +/spl pi//2) range is less than 0.5%. Total harmonic distortion measured for a fundamental frequency at 20 kHz and the next four harmonics is approximately 1%. This circuit could be used in several applications, including the AC excitation of bridge-type sensors as a replacement for sinusoidal oscillators.