Variable waveform synthesizer using digital circuitry

A variable waveform synthesizer for generating a variety of analog waveform approximations comprising:

• first pulse generating means for generating a digital pulse train of a predetermined period, T, the first generating means including means for varying the repetition rate of said pulse train;
• second pulse generating means responsive to said first pulse generating means for generating a pulse having a pulse width less than T for each pulse contained in the digital pulse train, the second pulse generating means including means for varying the pulse width of the pulses generated thereby;
• binary counter means responsive to the first pulse generating means and capable of sequentially attaining N separate and distinct digital states;
• decoding means responsive to said binary counter for decoding each of the digital states attained by the binary counter, said decoding means having at most N individual outputs each of which activated in response to one and only one of the N states attained by the binary counter means;
• combining means responsive to the decoding means outputs and the second pulse generating means and having at most N combining means outputs activated by coincidence between the decoding means outputs and the second pulse generating means;
• a plurality of constant current sources responsive to the combining means outputs such that when a combining means output is activated the current source coupled thereto is placed in a conducting state causing a current to flow therefrom, each of the current sources including means for varying the current provided thereby;
• and
• output means for receiving and combining the current produced by the current sources and synthesizing therefrom the analog waveform approximation, the output means including integrating means for shaping the analog waveform approximation.