Programmable frequency sine wave signal generator

摘要

A programmable frequency sine wave signal generator, including a generator for generating square-wave signals having a programmable frequency; a counter for counting the periods of the square-wave signals; circuits for providing successive discrete sine wave values from successive states of the counter; and a low-pass filter receiving the successive discrete sine wave values and providing the sine wave. The low- pass filter is a switched-capacitor filter with a switching mode that is controlled by a signal having a frequency proportional to the frequency of the square-wave signal. Correct selection of the values of the filter capacitors allows the cut-off frequency of the filter to be continuously substantially the same as the frequency of the sine wave.