Waveform shaping techniques for the design of signal sources

A new circuit technique is described for the generation of a sinusoid from a triangle waveform based on the addition of suitably proportioned current trapezoids. Undesirable operating characteristics, particularly peak and crossover distortion associated with previously reported methods, are reduced to more tolerable levels in a fully temperature-compensated design. An optimum breakpoint and distortion analysis is developed for establishing the design method and estimating the performance of the circuit. Measurements made on the prototypes indicate that a total harmonic distortion of better than 0.2% is readily attainable, whilst the non-saturating transistor circuit design offers considerable potential at high frequencies. The technique is readily amenable to the thick-film process with the modest spread of resistor values, and the absence of any tedious setting-up procedure makes the circuit particularly attractive to the user.