GB1385788A - Digital to analogue converter - Google Patents

Abstract

1385788 Digital to analogue converter TAKEDA RIKEN INDUSTRY CO Ltd 23 June 1972 [25 June 1971] 29500/72 Heading G4H In a digital to analogue converter, clock pulses are fed to two divider circuits, each dividing by the same number, the relative phase of the outputs being controlled by the digital input. The output pulses of the dividers set and reset respectively a bi-stable circuit and the output, pulse width modulated waveform is used to switch a reference voltage which, after filtering gives the analogue output. The digital input is applied to inputs 17a to 17n of AND gates 16a to 16n. Clock pulses of repetition period At are generated at 11 and are divided by n s in dividers 12 and 14. The output of divider 12 resets bistable 15 and enables AND gates 16a to 16n. If the applied digital value is n x (less than n s ), this is applied to frequency divider 14 which effectively counts from n x up to n s when an output pulse is produced which sets bi-stable 15. The two dividers thus operate out of phase by time n x .At and the output of bi-stable 15 is a pulse train of repetition period n s .At and "high output" period n x .At. This pulse train is applied to switch 18 and switches standard voltage e s (19) giving a corresponding waveform which after averaging by filter circuit 20, is the analogue output (n x )/(n s ).e s .