Pulse width modulated, push/pull digital to analog converter

摘要

A pulse width modulated digital-to-analog converter for utilization in low voltage, integrated circuit speech synthesis circuitry. A digitally programmable shift register is utilized to generate a pulse, which is generally related to the magnitude of a digital signal. A programmable delay circuit provides finer resolution by converting the least significant digital bits of data into pulse width information of shorter duration than the minimum pulse width generated by the controllable shift register. Pulse width information generated by the shift register and delay circuit is applied to the bases of two crossconnected transistors to drive a speaker or voice coil.